ML17209A325

Response Time of Platinum Resistance Thermometers Using Loop Current Step Response Techniques

ML17209A325
Person / Time
Site:	Saint Lucie
Issue date:	04/19/1978
From:	Jackie Jones, Mott J, Jay Robinson TECHNOLOGY FOR ENERGY CORP.
To:
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ML17209A324	List: ML17209A323 ML17209A325
References
R-8007, NUDOCS 8011070467
Download: ML17209A325 (104)

Text

Technology for Energy Corporation 10431 Lexington Drive Knoxville, Tennessee 37922

1

'I L

I'

RESPONSE

TIME OF PLATINUM RESISTANCE THERMOMETERS USING LOOP CURRENT STEP

RESPONSE

TECHNIQUES Prepared by J.

E. Mott J.

C. Robinson J.

E. Jones M. V. Mathis R. K. Fisher April 19, 1978

'I

l' C.T

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Certain informat n contained in this documen has been stamped "PROPRIETARY INFORMA N NOT TO BE DISCLO D WITHOUT WRITTEN AUTHO-RIZATION BY TEC".

The pu aser may se such information with his organization as needed to supp the use of TEC supplied equipment and analytical techniques b

shall ot disclose the information to third parties.

Howev

, the proprie ry information may be dis-closed to government regulatory agencies bu hall be withheld from public disclosur

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TABLE OF CONTENTS PAGE 1 ~

INTRODUCTION

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1.1 Scope of Investigation

l. 2

Background

2.

THERMAL ANALYSIS OF A ONE-DIMENSIONAL THREE REGION RTD

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2.1 Plunge Test 2.2 LCSR Test 2-1 2-4 3.

TIME CONSTANT DETERMINATION 3.1 LCSR Lumped Parameter Transformation 3.2 Alternate Method for Determining Time Constants 4.

DATA ACQUISITION INSTRUtKNTATION AND MEASUREMENTS 4.1 Data Acquisition Instrumentation 4.2 LSCR Measurements 5.

LCSR TEST DATA REDUCTION AND ANALYSIS 5.1 Time Shifting to Improve Results 5.2 Averaging to Reduce Noise 3-1 3-2 4-1 4-1 4-3 5-1 5-1 5-2 5.3 Analysis Sensitivity 5.4 Typical Numerical Examples 6.

CONCLUSIONS.

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5-4 6-1 7o REFERENCES e

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7-1 APPENDIX A Sections 1-3 OPS 781100-1 Operations and Service Manual.

A-1

LIST OF FIGURES FIGURE PAGE 2.1 RTD Construction 2-2 3.1 Time Constant Error Due to Finite Number of Eigenvalues 3-3 3.2 Oxide Thermal Conductivity 3-6 4.1 LCSR Measurement Instrumentation 4-2 5.1 Typical Output of an RTD Following a Step Change in Current from 2.2 ma to 35 ma 5-6 5.2 Average LCSR Test Results for 14 Steps 5-7 5.3 Typical Plunge Results Construction from LCSR Test Via Eqs.

5-8

LIST OF TABLES TABLE PAGE 5.1 Effect of to (Initial Time for Analysis) on the Time Constant 5-6 5.2 Effect of Signal to Noise Ratio on the Time Constant 5-7

1.

INTRODUCTION 1.1 Sco e of Investi ation The purpose of this report is to present both theoretical investiga-tions and typical measurement results of Loop Current Step

Response

(LCSR) measurements carried out on platinum resistance thermometers (RTDs) in-situ.

The LCSR tests were carried out by Technology for Energy Corporation (TEC) personnel under contract with several reactor owners and operators.

The objective of the test is to determine the time constant of RTDs using the In-Situ LCSR testing technique. 1,2 The method employed in these tests was the Loop Current Step 1

2

Response

technique. 'his requires a sudden change in the current going through the RTD.

The resulting ohmic heating of the RTDs was monitored using specially designed TEC instrumentation and recorded on a high quality multichannel FM tape recorder.

The results from the LCSR tests were subsequently reduced off site using TEC developed software on the TEC minicomputer system.

The eigenvalues obtained from the test were used to construct an equivalent plunge test.

Basically, the sensor time constant was taken as that time required for the sensor (RTD) to reach 63% of its final steady state reading following the analytically constructed plunge test.

The Nuclear Regulatory Commission has recommended that operators of nuclear power plants carry out sensor time response verification for those sensors included in the plant protection system.

In Pcs, this 3

includes the RTDs monitoring the inlet and exit temperatures of the reactor.

Since the RTDs are located in thermal wells or in bypass lines,

1-2 it was deemed necessary to carry out these measuremnts in-situ.

For the RTDs, it was judged -that the LCSR testing methods being developed at ORNL (see e.g.,

Ref.

2) for thermocouple testing in the fast reactor program may be applicable to RTDs.

Accordingly, EPRI has funded a research l

program at The University of Tennessee for establishing the applicability of LCSR testing techniques for in-situ time response testing of RTDs.

TEC has extended the EPRI research program by (a) developing specialized instrumentation for safely implementing LCSR tests, (b) developing analytical techniques to overcome bias errors inherent in the lumped parameter transformation, and (c) establishing methods to improve the limited signal-to-noise ratios which will be present in all operating systems.

The instrumentation and techniques employed by TEC are described throughout this report.

l

2.

THERMAL ANALYSIS OF A ONE-DIMENSIONAL THREE REGION RTD In the following, we present the thermal analysis of a one-dimensional three region RTD.

Fig. 2.1 shows a cross section of a typical sensor.

The inner region is normally a ceramic material with the platinum sensing element imbedded at radius R.

This oxide region is surrounded by a metallic sheath to form the sensor.

Normally, the sensor is then inserted into a well mounted in a pipe with the well perpendicular to the flow of the fluid whose temperature is to be measured.

The gap, 6, between the RTD and the well is a result of manufacturing tolerances.

The time response of an RTD, initially at uniform temperature T0 plunged into a fluid whose temperature is zero, is given by the solution of 2.1 where the subscript i indicates the region in the RTD.

The solution to Eq. 2.1 is given by i

p.t

=$ C.

Z (M

) eJ T

j oi ij r4 0

2.2 where Z

=A. J

+B Y

oi i

o i o'

. =~33 P.j r4 2.3 2.4 2-1

2-2 Air Gap 6

r r-R~

r+

1 I

y

/

mzH

~ l I

II I /

A l

i Platinum Sensing Element (R)

//

WELL E

Oxide Steel or Inconel Pig. 2.1 RTD Construction (typical)

2-3 and J and Y are Bessel functions, of the first and second kind.

The eigenvalues M.. are related s'nce the decay coefficients p. must be ig the same for each region, thus M

2.5 The values of A., 3 and M.. are determined by the following boundary ij conditions:

aT Br

=Oor T

(r =0) 1 1

r=r1 2.6 Tl( 2)

T2 (r2) 2.7 aT

-k1 3r r~l 2 aT2

= -k2 Br r=r2 2.8 aTZ

-k 2 3r aT3 k

r3 3 Br r=r3'.9 T2 ki

-k

~

(T (r) -T(r)),

2 Br 6

2 3

3 3

2.10 and aT3

-k 3 3r

= h T3(r~).

r~

2.11 The coefficients C. are functions of the initial conditions only and may j

be evaluated using the orthogonality condition rf pC.

Z (M

)

Z.(M.

) rdr =0 (j 4k).

ii oi ij r oi ikr

'1 2.12

2-4 Eq. 2.2 may now be used to evaluate the time response of the platinum sensing element at radius R.

Here T (R) p.t e~

To j

wi'th A C

Z01(M1

)

o R

j j

01 lj r4 2.13 2.14 2.2 LCSR Test

. The temperature distribution of an RTD, initially at uniform temperature

zero, immersed in a fluid also at zero temperature, subjected to a step input of heat at R, caused by a step increase in current in the platinum sensing element is given by the solution of BT.

q p

C BT.

(r

) +-

r Br Br k.

k Bt

2. 15 where q

is the rate at which ohmic heat is generated per unit volume by the electrical current passing through the platinum wire.

The temperature may be decomposed into two components )

and T

, where. T.

~'f is the temperature distribution at time equal to infinity and is given by the solution of 1B

'f (r

) +q/k 0.

.r Br Br i i 2.16 The residual P. satisfies. the equation i

1B (r

)

=

r Br Br ki Bt

2. 17

and is subject to the boundary conditions given by Eqs.

2.6 through 2.11.

The solution of Eq.

2.15 for a current step is given by p

T(r) =T. (r)+)D. Z.

(M.

) ej i

if

. j oi ij r~

2.18 with D. determined by the initial condition P (t=0) = -T j

i if The important result of this analysis is that the decay coefficients, p., are the same for the current step as for the plunge.

Thus, if they j're obtained from a LCSR test, then only the coefficients, A, are lacking in Eq.

2.13 which determines the response of the RTD to a step change in coolant temperature.

3.

TIME CONSTANT DETERMINATION In the preceding section, it was shown for a one-dimension sensor the eigenvalues, p., are the same for the plunge., and the j'urrent step.

In the following, we will describe the LCSR lumped parameter transformation method for determining the values of the coefficients, A

The limitations of this method will be shown and an alternate method will be presented which improves the estimates of the RTD time constant.

3.1 LCSR Lum ed Parameter Transformation 1,4 A nodal model has been developed by Kerlin 'hich describes both a plunge test and an LCSR test.

This analysis makes the following assumptions:

1.

The heat flow is one-dimensional, and 2.

The sensing element is located at the central node (i.e.,

R = rl in Fig. 2.1).

Prom this model, Kerlin found the response of the sensing element in a plunge test of an RTD to be given by N

p.t T(r,t) ~

)

K e j=l 3.1 with the coefficient given by 1

j Pj(p- - pl) (p P2)"

(Pj PN) 3.2 k

Me note that in the limit as N (the number of eigenvalues found from the current step) approaches infinity, K. approaches C.

(Eq. 2.2).. The major j

j 3-1

0

3-2 drawback in the use of Eqs.

3'.1 and 3.2 to obtain the time constant of an RTD is the inability to extract more than two or three eigenvalues, p.,

from a real current step test.

Fig. 3.1 shows the error in time constants due to the limited number of eigenvalues available for a variety of RTDs. It is important to note that this error is always positive.

The nodal LCSR lumped parameter transformation, Eqs.

3.1 and 3.2, thus produces a time con-stant that is less than the true value and consequently predicts a

faster response to a transient than the sensor can actually achieve.

Fig. 3.1 also shows that there is no constant factor which may be used to correct the result of the transformation.

A second error in the time constant determined by the LCSR trans-formation is its failure to account for the location of the sensing ele-ment.

This error is negative since a sensing element located near the outer suface responds faster than one located at the center.

A significant feature of the nodal LCSR transformation is that it does not require any knowledge of the RTD geometry or its thermal properties.

In the following section, we will describe an alternate method which utilizes known information to improve the estimates of the time constant of an RTD.

3.2 Alternate Method for Determinin Time Constants Eq. 2.2 can, in principle, be used to determine the time constant of an RTD.

This, however, requires the accurate knowledge of the dimen-sions and the thermal properties for all regions of the sensor.

In'eneral, we PROPRIETARY INFORt4ATION NOT TO BE DISCLOSED WITHOUT WRITTEN AUTHORIZATIONBY TEG

3-3

A J

do not know all of these properties accurately and, in fact, it is changes in these parameters which cause sensor time response degradation.

The parameters generally known are:

l.

Thermal properties of the sheath and well materials,

and, 2.

Sensor dimensions and corresponding uncertainties due to manufacturing tolerances.

The principal unknowns are:

1.

thermal properties of region 1, 2.

surface heat transfer coefficient, h, and 3.

gap width, 6.

The thermal conductivity of the ceramic is of principle concern.

I It can vary, a factor of ten or more due to cracking, separation from the sheath, or poor (or no) oxide packing. around the ceramic element.

The unknown surface heat transfer coefficient and gap width are nearly equivalent since both are purely resistive elements with no energy storage and are outside region l.

One method of accounting for both is to define an equivalent heat transfer coefficient by the relation 1

eq 1

h kair 3.3 A better approximation is to decompose the surface heat transfer resistance into a normal resistance which can be calculated as a function of Reynolds and Prandtls numbers and an unknown resistance which is caused by fouling or other phenomena which degrade RTD performance.

This additional resistance is now added to the gap resistance and an equivalent gap thickness is defined by

= 8+k xRdd eq air added' ROP RIETARY INFORMATION NOT TO BE DISCLOSED WITHOUT

.NRITTEN AUTHORIZATIONBY TEC 3.4

3-5 The unknown parameters;required to evaluate Eq.

2.2 are now the effective thermal conductivity of the oxide and the equivalent gap thickness.

Figure 3.2 shows 'the first two eigenvalues as a function of the oxide conductivity and the gap width."

We note the first eigenvalue is predominantly a function of the gap width while the second eigenvalue depends primarily on the thermal conducitivity of the ceramic.

Vie can now establish a rationale for determining the plunge time constant's from knowledge of the first two eigenvalues as determined by the LCSR test, together, with physical dimensions and thermal, propertiesof the sheath and well.

The method employed in the alternate technique is as follows:

1.

Determine the first two eigenvalues from a fit to the LCSR test data, 2.

Estimate the thermal conductivity of the ceramic and the gap width and calculate the eigenvalues that satisfy boundary conditions 'given by Eqs.

2.6 through 2.11.

3.

Compare these eigenvalues with those determined by test data, 4.

Adjust the thermal conductivity and gap width and repeat steps 2 and 3 until the eigenvalues

agree, 5.

Using these values, compute.

C. and A. and the time required for j

j the, temperature sensing element to reach 63% of its final temperature following a plunge.

The time constant of the sensor is taken to be the time computed in step 5.

This procedure has a significant advantage over the LCSR transformation (described in Sect.

3.1) in that it utilizes all available information to ob-

'*The format for this figure was suggested by Richard Shamblin of FPL.

Pr(QP RtETARY le FORMATlON NOT TO BE DISCLOSEO )YITHOUT YIRITTEH AUTHORIZATION BY TEG I

1' 3-6

.2

.3

.4

.5

.6

.7

.8

.9 I

I I

I I

I t

I

~

1.0 1.1 1-2

~

~

I 0.5 0.50 0..4

0. 75 0.3

1. 00 I

~

I I

I ~

~

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~

1.25 CC 1.50 0.2 1.75 2.00 0.15

'2. 25 2.50

.08

.12

.16

.20

.24

.28

.32 Oxide Thermal Conductivity (k, BTU/HR-FT-F)

Figure 3.2 Relationship between Ay and A2 (eigenvalues) with Various Air Gap and Oxide Thermal Conductivity Parameters.

P ROP RlETARY lHFORt4ATlON NOT TO BE DISCLOSED WITHOUT WRITTEN AUTHORIZATIONBY TEG

3-7 tain the best estimate of the time constant and thereby eliminates the non-conservative bias error introduced by the finite number of eigenvalues.

It also takes credit for the location of the sensing element.

This procedure allows the user to systematically determine the effect of uncertainties in geometry and in thermal properties on the time constant.

The user can thereby assign appropriate error limits on the resultant time constant.

P BOP RlETARY lNFORMATION NOT TO BE DISGLOSEO WITHOUT WRITTEN AUTHORIZATIONBY TEG

4.

DATA ACQUISITION INSTREKNTATION AND MEASUREMENTS 4.1 Data Ac uisition Instrumentation For purposes of the LCSR measurements, special instrumentation was

designed, fabricated, and tested by TEC.

A block diagram of the LCSR test instrumentation is presented in Fig. 4.1.

This rack mounted modular instrumentation system consisted of a TEC Model 1131 Constant Current Source, Model 1121 Control Module, and Model 1101 LCSR Bridge.

In addition, three separate modular power sources were utilized to:

(1) provide a floating excitation voltage for the bridge (relative to the signal conditioning circuitry), (2) power the control and switching logic, and (3) provide the normal instrumentation power for signal conditioning.

The RTD under test was interfaced with the Model 1101 LCSR bridge via a special 3-wire test cable.

During an LCSR test, a small standby current is furnished the RTD from the Model 1131 constant current source.

Upon the initiation of the LCSR step (controlled from the Model 1121 Control Unit), a controlled step in RTD current is made and the output from the Model 1101 LCSR Bridge is recorded on a FM tape recorder along with a signal from the Model 1121 Control Unit (Step Output).

During these tests, automatic control of the LCSR steps can be executed using an external function generator or computer.

The recorded signals can be later analyzed off-line using an appropriately programmed minicomputer based analysis system.

Special software programs are employed to determine the RTD time constant and are described in Sect.

5.

4-1

odule Powe Bridge Power Supply Model 1131 Constant Curren Source Model 1101 LCSR Bridge i nal Conditioni g LCSR Output 3-Hire Test Cable RTD Under Test Control Power Model 1121 Control Unit Pulse Output FM Tape Recorder Function Generator Auto Step Input Fig. 4.1 LCSR Measurement Instrumentation.

4-3 4.2 LCSR Measurements LCSR measurements are performed using the TEC designed instrumentation in accordance with Sect.

3 of the appropriate Operations and Service Manual (Appendix A).

Here, preoperational and calibration tests are performed using a test resistor to simulate the RTD element.

After the instrumentation is verified to be operating properly, the actual RTD Testing Procedure, as outlined in Appendix A, Sect.

3.4 is performed.

LCSR data from

>~10 steps are recorded for off-line data reduction and analysis as described in Sect.

5. If a minicomputer, is available,'hen an-line, data reduction using the special TEC LCSR software package can be carried out.

4

5.

LCSR TEST DATA REDUCTION AND ANALYSIS After performing the LCSR test for an RTD, the results of this test must be analyzed to determine the eigenvalues (exponentials) present in the RTD response.

The computer program used for this analysis finds the eigenvalues p

such that the sum-squared error defined by 5.1 is minimized, where y is the LCSR response and a.'are fitted coefficients.

Limitations on this fitting procedure will be described and techniques for improving analysis results will be presented.

5.1 Time Shiftin to Im rove Results A problem that must be overcome in fitting an LCSR test is that only three exponentials can normally be resolved due to restrictions of digitization resqlution, computer memory, and analysis time.

Actually, an LCSR response consists of an infinite number of exponentials, but only the slowest two or three are necessary for the analysis.

To minimize the contamination effects of fast exponentials on the exponen'tials of interest, these fast transients must be eliminated.

The easiest technique for eliminating fast exponential is to skip the early part of the test until they have decayed to become smaller than the analysis can resolve.

A problem with this technique is that the slower exponentials are also decaying over the time skipped and even though their decay is slower, some resolution from the digitized data is lost.

5-1 P ROP RIETARY INFORMATION NOT TO BE DISCLOSEO WITHOUT WRITTEN AUTHORIZATIONBY TEG

5-2 The span of time to skip to eliminate higher eigenvalue effects (faster exponentials) becomes a trade-off between the rate of decay of fast exponentials and the loss of resolution in the data of interest.

For most RTDs, the time constant is given approximately by v = 1.5/(-p )

where pl is the first eigenvalue.

The ratio between the fourth and first eigenvalue (p

i8 ~

5

~l Typical Output of an RTD Pollo~zin,o, a Step Change in Current from 2.2 ma to 35 ma.

S

'l 0

5a9

~,

5 0

cl 3

0 CI 0oe 0 ~ 0 0

~

0 ~ ~ ~ 00 ~ ~ ~ ~ ~ ~ ~ ~

0

~ ooroo ~ ~ jo ~ 000 ~ ~ ~

0

~ ~ ~ ~ rrrooo ~ eo ~ ~ 00 ~ ~

0 0

ro ~

0 ~ 0 0 0 0 0 ~ 0 0 0 0 ~ ~ 0

~f ~ ~ ~ to ~ ~ r jr ~ ~ ~ ~ ~ ~ ~

0

~ % ~ ~ ~ 00 ~ ~ ~ E ~ ~ ~ ~ 0 ~ rr ro ~ oo ~ rtott ~ 0 ~ ooort rf 0 ~ ore ~ orf000 ~ 00 ~ 0 0

~) ~ or 0 ~ 00 ~) 0 ~ ~ 0 ~ ~ ~ ~

e 000 ~ 00000 ~ 0 ~

000 j ~ oeooo 0

0 ooofoe too 000 rreoot It ~ ~ t ~ ~ ~ ~ re ~ 0

~ 0 ~ ~ t ~ or )>> ~ ~ 0 0 ~ ~ ~

~ ~ 00 ~ \\ ~ ~ ~

0 r

of000000004000

~ ~ ~ rkorrroro 0

re\\00 ~ ~ ~ 00 oe 0 ~ 0 ~ ~ re Orr ~ 0 ~ 0 ~

0 0

t 0 0t 0 ~ 0 j0 ~ ~ 0 0 ~ ~ ~ qr ~ 0 0 ~ 0 ~ ~ 00t 0 ~ 0 0 0 ~ >>

0000 ~ 00 frooooot ~ Peer

~ ~ ~ ortho ~ ro ~ ~ 0 0

00 0 ~ 0 0 0 0 0 ao ~ ~ ~ 0 0 ~ ~ oe ~ ~ ~ ~ ~ 0 00 0 0 0 0 0 0 ~

0 ~ 0 0 0 0 0P 0 ~ 0 t 0 0 0 Q 0 0 0 ~ ~ ~ 0 of 0 ~ t 0 ~ 0 0

~

e0 0

0 00 0 0 0 0 0 (0 ~ ~ ~ ~ 0 0 0 (0 ~ 0 ~ ~ o 0 0+ 0 0 0 ~ 0 0 0

~ ~ ~

) ~ ~

~ ~ 0

~ 0 ~

j

~

0 I ~ ~

~ 0 0

~ ~ 0 fee 0 ~ 00 0 oe 0 0000 000 0 j ~

000 ~ ~

0 ~ 00 00 ~ 0 00 oo re ~ot 0

oooo jo 0 ~

Oeroo fr

~t 0 0 0 0 ~ 0 00 ~ 0 000 0000 00 (000 ~ 0000 0 ~ 0 00 0 f0 r 0 0 0 0 0 0 0

~ 0 ~ ~ 0 0 et ~ 0 0 0 0 0 0

~ ~ 0 0 0 0 $ 0 0 0 0 00 0 0 0

0 0 ~ 000 ~ fooeeoooo 0 0 ~ 0 0 0 Oe 0 0 0 ~ 0 0 0

~ 0 0 0 0 0 fo 0 0 0 0 o0 0 otter (00000000

+OO 00 0 ~

f (0 OO OO 0'0 4 ao ttoo f

+aae

~ 0 0 0

pate ~ 00 poeeet 0

oa+ot 0 0 0 joaroooe Oeee ~ 0 0

.-3:

12 18 21 24 27 30 Time in Seconds Fig. 5.2 Average LCSR Test Results for 14 steps.

5-10 LCSR Te 00 ~ 0 0 0B~1 st

~ 0 ~ 0 ~ 0

~ ~ ~

~

~ ~

~ ~ ~ ~ ~ ~

~ ~ 0 ~

00 ~ 0

~ ~ 0 ~

~

~ ~ ~ ~ ~

~

~ 0

~ ~

~ 0

~

~ ~

~

~

~ ~ 0 ~

0

~ t% 0 0

~ ~

0 0

~ Cons t:rue ted:P lunge Test Transient

~

~ 0

~

~

0 ~

~

~

~

0 0 0

~ ~

040 0

0

~ 0 ~

.i.

0 0

0 0 ~

~ ~ ~ ~ ~

0 0

~

~ 0

~ j0 ~ 000 ~ 0

~ 0 ~

~ 0 ~

~ ~

~

~

0 000

~

0 0

~

~

~

~

~ ~ ~ ~ ~ 0 0 ~ ~

0

~ 0

~ ~ ~ ~ 0 I

~l ~ ~ ~

~ 0000 ~ ~ ~ I 0

~

0 \\

0 ~ ~ ~ 0 ~

0 0 ~ 0 0

0 0 ~ 000 ~ ~

~ ~ ~ ~

~

~-

0000 ~ 000 f00

~

000 0 ~ 0 ~ ~ 0001 0 ~ 0000 0

~ 0 ~ 00000 g 0000 0

3 6

9 12 15 18 21 24 27 Time in Seconds 30 Fig. 5. 3.

Typical Plunge Results Constructed from LCSR Test. Via Eq. 2. 2.

6.

CONCLUSIONS It has been demonstrated that the time constant for Platinum Resistance Thermometers can be extracted from carefully performed in-situ LCSR Test results under normal plant operation conditions in PWRs.

It generally will be necessary to employ averaging of the results obtained from several tests to acquire an acceptable signal-to-noise ratio prior to extracting eigenvalues from the LCSR test results.

Generally, it will be possible to extract two to three eigenvalues from the averaged LCSR test results.

Mith this limited number of eigenvalues, it was demonstrated that the application of the nodal model transformation from LCSR test results to the equivalent plunge test results would lead to a bias error in the inferred time constant (a time constant would be obtained which is smaller than the actual time constant).

To eliminate this bias error, a transformation was developed by TEC which employ's a physical model.

In this new transformation, the results from the. LCSR test are used to identify the physical properties (thermal conductivi.ty of the oxide and the air gap K

or film resistance) which are least

known, and the remaining physical properties are assumed to be known.

This transformation technique has been shown to be free of the bias errors associated with the nodal model (which utilizes no known physical properties).

In addition to eliminating the bias error, this new transformation permits the analyst to properly account (take credit) for the decrease in time constant which occurs when the sensing element is located near the surface of the RTD.

6-1

6-2 When carrying out a LCSR test, it is imperative that the maximum current be much less than the current which can damage the sensor.

The signal-to-noise ratio increases linearly with the magnitude of the current.

Thus, we have conflicting requirements on the amount of current we supply to the sensor, i.e.

we 'do not wish to damage the sensor, but we cannot properly interpret the results if the signal-to-noise ratio -is small.

We at TEC use repeated tests (averaging) to obtain the desired signal-to-noise ratio and the maximum current is, selected so that the integrity of the sensor is maintained.

To accomplish the averaging, it is important that the instruments being used have a very low temperature coefficient and a high degree of repeatibility.

Thus, TEC has designed a special LCSR test instru-mentation package which meets 'these requirements.

7.

REFEPZNCES 1.

'T.

W. Kerlin, et al., "In-Situ Response Time Testing of Platinum Resistance Thermometers," Electric Power Research Institute report EPRI

~ NP-459 (January 1977).

2.

R.

M. Carroll and R. L. Shepard, "Measurement of the Transient

Response

of Thermocouples and Resistance Thermometers Using an In-Situ Method,"

ERDA report ORNL/TM-4573 (June 1977).

3.

Regulatory Guide 1.118 Periodic Testing of Electric Power and Protection

Systems, U.

S. Nuclear Regulatory Comm'ssion (Rev., 1, November 1977).

4.

T.

W. Kerlin, "Analytical Methods for Interpreting In Situ Measurements

~of Response Times in Thermocouples and Resistance Thermometers,"

ORNL-TM-4912 (March 1976);

7-1

~

~

APPENDIX A SECTIONS 1-3 OPS 781100-1 OPERATIONS AND SERVICE MANUAL

OPS 781100-1 TEC MODEL 1100 LCSR TEST INSTRUMENTATION OPERATIONS AND SERVICE MANUAL February 1978

TABLE OF CONTENTS PAGE 1.

INTRODUCTION TO LCSR MEASUREMENTS

. 1-1 2.

SPECIFICATIONS AND BRIEF DESCRIPTION

. 2-1 2.1 TEC Model 1100 LCSR Test Instrumentation

. 2-1 2.1.1 Specifications for TEC Model 1131 Constant Current odule

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~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

~

M 2-4 2.1.2 Specifications for TEC Model 1121 Control Module 2.1.3 Specifications for TEC Model 1101 LCSR Bridge/Amplifier Module 2.1.4 Specifications for TEC 'Model 934 Power Bin 3.

OPERATING INSTRUCTIONS 2-4 2-5 2-6

~

3 1 3.1 Operating Voltage and Safety Information 3.2 Functions of Controls, Connectors, and Indicators

~

3 1

~

3 3

3. 2. 1 TEC Model 1131 Constant Current Module e

~

~

~

e i

i r 3-3 3.2.2 TEC Model 1121 Control Module 3.2.3 TEC Model 1101 LCSR Bridge/Amplifier Module 3.2.4 TEC Model 934 Power Bin 3.3 System Pre-Operational Test and Turn-On Procedure 3.3.1 Procedure 3.4 RTD Testing Procedure Utilizing the Model 1100 Series LCSR Instrumentation

/

3.4.1 Procedure

~

3 3

3-6 3-8 3-8 3-10 3-14 3-15

I 0

PAGE 4.

SPECIAL TESTS AND ADJUSTMENTS 4-1 4.1 TEC Model 1131 Constant Current Module 4.2 TEC Model 1121 Control Module 4.3 TEC Model 1101 LCSR Bridge/Amplifier Module 4.4 TEC Model 934 Power Bin 4-1 4-1 4-2 4-2 5-COMPONENT LOCATIONS AND LCSR INSTRRiENTATION DRAWINGS

~

5 1

APPENDIXES A.

DETERMINING RTD RESISTANCE VALUES WITH THE MODEL 1101 LCSR BRIDGE/AMPLIFIER MODULE

. A-1 B.

LCSR SOFTWARE DESCRIPTION

. B-1

l.

INTRODUCTION TO LCSR MEASURE1KNTS The Loop-Current Step

Response

(LCSR) method was developed to measure in-situ the transient response of a thermocouple or a resistance thermometer.

A step change is made in the ohmic heating of the sensors at time zero and the time dependence of the heating (or cooling) is analyzed to determine the time constant of the sensor.

In particular, results from the LCSR measurements are used to'predict the response of the sensor to a step change in the temperature of the medium which the sensor is monitoring.

The time constant of the sensor is taken to be that time required for the sensor to obtain 63.2% of its final steady state reading following the step change in temperature of the medium in which the sensor is located.

For the resistance thermometer (RTD), the procedure is to make a step increase in ohmic heating at time zero.

The RTD is in a bridge circuit which is balanced prior to the step in ohmic heating at time zero.

Then the resistance (voltage) versus time transient data obtained following a step increase in current through the bridge at time zero is analyzed.

In particular, an equation of the form is fit to the transient data (generally a microprocesser is employed for the fitting).

The poles

p. are the roots to the characteristic equation 3

describing the sensor.

Having the roots to the characteristic

equation, either nodal or distributed parameter models are employed to construct the response of the sensor to a simulated step change in the temperature of the medium being monitored.

1-2 The TEC Model 1100 LCSR Test Instrumentation is designed for carrying out the LCSR test on RTDs simply and safely.

A constant current source is employed to drive the bridge with capability of supplying a step "change in current through the bridge via manual or automated control.

The unbalance voltage of the bridge induced by the RTD resistance change is fed into a true differential amplifier with variable gain to acquire the desired voltage versus time transient data following the step change in ohmic heating.

In addition to the output voltage of the bridge/amplifier module, an adjustable logic signal is available as an output from the control module as a "high" during high current through the bridge and a "low" during low or standby current through the bridge.

2.

SPECIFICATIONS AND BRIEF DESCRIPTION 2.1 TEC Model'1100 LCSR Test Instrumentation The TEC Model 1100 Rack Mounted Modular LCSR Test Instrumentation system shown in Fig. 2.1 consists of 3-modules a

TEC Model 1131 Constant Current Module, Model 1121 Control Module, and Model 1101 LCSR Bridge/

Amplifier Module all housed in a TEC Model 934 Power Bin.

The power bin contains three separate power sources to:

(1) provide a floating excitation voltage for the bridge (relative to the signal conditioning circuitry),

(2) provide control and switching logic power, and (3) provide the normal instrumentation power for signal conditioning.

The system is also provided with a 25 ft. 3-wire shielded test cable for interfacing with an installed RTD.

Normally, an RTD is interfaced with the Model 1101 LCSR Bridge/Amplifier Module via'-the special" 3-wire test cable as shown in Fig. 2.2.

During an LCSR test, a small standby current is. furnished the RTD from the Model 1131 Constant Current Module.

Upon the initiation of the LCSR step (controlled from the Model 1121 Control Module),.a controlled step in RTD current is made and the output from the Model 1101 LCSR Bridge/Amplifier Module is provided for recording on an FH tape recorder (LGSR Output) along with a signal (Pulse Output) from'the Model 1121 Control Module.

Specifications for each of the modular components comprising the TEC Model LCSR Test Instrumentation as well as the power bin are discussed in Sects.

2.1.1 through 2.1.4.

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Figure 2.1 TEC Model 1100 Rack Mounted Modular LCSR Test Instrumentation.

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odule Powe Bridge Power Supply Model 1131 Constant Curren Module Model 1101 LCSR Bridge Amplifier Module i nal Conditioni LCSR Output 3-Wire Test Cable RTD Under Test Control Power Model 1121 Control hfodule Pulse Output FM Tape Recorder Auto Step Input Figure 2.2 LCSR Measurement Instrumentation.

2-4 2.1.1 S ecifications for TEC Model 1131 Constant Current Module.

Current Out ut Type Adjustable constant current floated with respect to ground Range 0-100 mA, front panel adjustable using 10 'turn vernier calibrated control Accuracy Linearity Ripple Temperature Coefficient Better than 2% of dial indication (20-100 mA)

Better than 1% (20.mA to 100 mA) 1 gA RMS

< 50 ppm/'C Overload Protection Current Output to LCSR Bridge Limited to 125 mA by fuses on both + and outputs Current Output, to Test Points Internally limited by 20 0 series output resistor 2.1.2 S ecifications for TEC Model 1121 Control Module.

Switchin Features Bridge Current Via dual reed relays with lifetime of > 10 6 operations Relays rated 8 500 mA or 16 VA Pulse Output Via single reed relay with lifetime of

> 10'perations Relay rated 8.250 mA or 8 VA Operational Modes Manual Single LCSR steps initiated and terminated by front panel control Auto Automatic sequential LCSR steps initiated by external square wave input from front panel mounted connector.

Input require-ments:

0 to 5 Vdc, 10 mA (TTL compatible),

< 10Hz

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2-5 Current Selection Bridge Current Polarity 3 positio'n toggle'switch controlled +/OFF/-

Bridge Current Division 16 selected ranges via 4-bit PC Board Mounted Switch providing current step ratios of 3 through 18 or 6 through 37 depending on RTD resistance Out ut Features Pulse Output Adjustable 0 to + 5 volts.

Output is zero when LCSR step is in low state, at preset value when LCSR step is in high state.

High Current Indicator Front panel mounted LED lights when LCSR step is in high state.

2.1.3 S ecifications for TEC Model 1101 LCSR Brid e/Am lifier Modu e

~

~Brid e Type Temperature Coefficient RTD Balancing Range Floating Wheats tone 0.1 ppm/mw-'C 105-545 ohms continuous via front panel coarse and fine balance 'controls.

No external decade box is re uired

~dm lifter Type Floating true differential Frequency

Response

(- 3 dB) dc to 70 kHz 8 G = 20 Slew Rate 12 V/u sec Gain 20, 50,

100, 200, 500 switch selectable from front panel Input Offset Drift Output Offset 3 3iv/'C Adjustable to zero via front panel adjustment

0

2-6 In ut Connection Test Cable Special low noise shielded 3-wire 25 ft.

test cable with special Amphenol keyed connector.

RTD end of cabl'e color coded with lugs for attaching to terminal screws.

2.1.4 S ecifications for TEC Model 934 Power Bin.

Brid e Power Output Voltage 40 Vdc within 2%

Output Current to Constant Current Source Output Ripple Source Voltage 600 mA 0.25 mV RMS max 115 Vac 8 60 Hz + 10%

Control and Di ital Switchin Power Output Voltage Output Current Output Ripple Source Voltage

+ 5 Vdc within 1%

500 mA 2.0 mV RMS max 115 Vac 8 60 Hz + 10%

Instrumentation Power Output Voltage Output Current Output Ripple Source Voltage

+ 15 Vdc within 1%

350 mA 2.0 mV RMS max 115 Vac 8 60 Hz

+

10%

0 0

3.

OPERATING INSTRUCTIONS 3.1 Ooeratin Volta e and Safet Information The TEC Model 1100 LCSR Test Instrumentation is designed to plug into three reserved slots provided in a TEC-934 Power Bin.

The slots reserved for these three modules are identified in Table 3.1.

WARNING Do not attempt to switch locations with these three units.

Keys have been provided in reserved slots to prevent plugging in the wrong module.

Also, due to interconnecting w'iring on the back-

plane, these modules will not operate 'in a non-reserved slot.

The slots behind the blank panels are wired for acceptance of other TEC modular instruments (TEC-901 Signal Conditioning Amplifier, etc.).

Operating Power is provided to each edge card connector as shown in Table 3.1.

The TEC-934 Power Bin operates from a single-phase 120 VAC power source with one of the current-carrying conductors (the neutral conductor) at ground (earth) potential.

Operation from power sources where both current-carrying conductors are live with respect to ground (such as phase-to-phase on a 3-wire system) is not recommended, since only the line conductor has over-current (fuse) protection within the power line.

The TEC-934 Power Bin has a 3-wire cord with a 3-terminal polarized plug for connection to the power source and safety-earth.

The ground terminal of the plug is directly connected to the metal parts of the power bin.

For electric-shock protection, insert this plug in a mating outlet with a safety-earth contact.

3-1

TABLE 3.1 934 POWER BIN EDGE CONNECTOR PIN ASSIGNMENT FROM RIGHT TO LEFT Pin J8 through J4 Unassi ned J3 1131 Module J2 1121 Module Jl 1101 Module B

E Chassis Ground

+ 15V

+ 15V Ground 5V Ground r

5V N

-V IN

+V IN I(-) OUT I(+) OUT I(+) IN I(-) IN I(+) OUT I RETURN I(+) IN I (RETURN)

S

3-18 ll.

Stop the recorder and record tape footage counter reading on the attached data sheet.

12.

Verify that the TEST DISABLE switch is in the DISABLE position then remove the RTD attached in step 6.

13.

Inform plant personnel that testing is completed and the RTD may be reconnected to the plant instrumentation.

h 0

3-3 3.2 Functions of Controls Connectors and Indicators Before you turn the TEC Model 934 Power Bin ON, read,this portion of the manual to familiarize yourself with the controls, connectors, and indicators shown on Figs. 2.1 and 3.1.

3.2.1 TEC Model 1131 Constant Current Module.

Front Panel (See Fig. 3.1) 1.

CURRENT ADJUST dial determines the amount of current fed to the Model 1121 Control Module.

The control is calibrated in mA and has a range of adjustability of 0 to 100 mA.

One half this

/

value is the maximum current ever applied to the RTD under test.

2.

+ test jacks are used to monitor the output current from the Model 1131 Constant Current'odule.

Card Mounted Components (see Fig. 3.2) l.

Fuses Fl and F2 are provided to limit the current from the Model 1131 Constant Current Module to

< 125 ma in order to protect the RTD in the event of a component breakdown.

3.2.2 TEC Model 1121 Control Module.

Front Panel (see Fig-3.1) 1.

HIGH CURRENT indicator is provided as an indication of when the LCSR step is at its high current level.

2.

PULSE OUTPUT jack provides a negative or positive going output pulse in sync with the LCSR step.

This pulse is normally used with the LCSR step to provide an initialization pulse for computer analysis.

3.

PULSE HEIGHT adjustment (through the front panel) varies the output from the PULSE OUTPUT jack from 5 to + 5 volts.

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1121, and 1131 LCSR Instrumentation Modules.

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3-6 4.

The BRIDGE CURRZNT +/OFF/- switch determines the polarity of the LCSR step as well as providing a means for removal of external bridge current power.

5.

The AUTO STEP INPUT jack provides a means of inputting a signal

~ from an external function generator to be used to control, the rate/duration of each LCSR step automatically.

6.

The AUTO/MANUALMODE switch determines the test mode for the LCSR instrumentation.

In the AUTO MODE, the input signal at I

the AUTO STEP INPUT jack determines the rate/duration of each LCSR step.

In the kfA'lUAL MODE, the rate/duration of each LCSR step is determined by manual control of the TEST/DISABLE switch.

7.

The TEST/DISABLE switch determines when and whether an LCSR step is begun, MANUAL and AUTO modes respectively.

Board Mounted Controls (see Fig. 3.3) 8.

BRIDGE CURRENT DIVIDER switch (Sl-4) determines the step current ratio used for each LCSR test.

The use of this switch is fully described in Sect.

3.3.

3.2.3 TEC Model 1101 LCSR Brid e/Am lifier Module.

Front Panel (see Fig. 3.1) 1.

The TEST RTD input jack mates with the special three-wire.(shielded) interface cable provided to interface with two or three wire RTDs.

2.

COARSE BALANCE switch acts as a range switch, providing a means of properly balancing the LCSR bridge with RTDs of different resistances (105-545 ohms).

3.

FINE BALANCE control is the fine vernier control for properly balancing the LCSR bridge with the RTD under test.

NOTE:

Approximate value of RTD resistance under balanced conditions may be obtained by use of the tables given in Appendix A for the appropriate dial settings.

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TEC Model 1121 Control Module.

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3-8 4.

GAIN switch determines the gain (20, 50,

100, 200, or 500) of the signal conditioning portion of the Model 1101 LCSR Bridge/Amplifier Module.

5.

LCSR OUTPUT jack" provides the output signal for the LCSR test.

This signal is normally recorded along with a sync pulse (PULSE OUTPUT) for later off line analysis using a micro-or minicomputer equipped with special TEC designed software.

6.

OFFSET control is provided to DC zero the final amplifier in the signal conditioning portion of the module.

Board Mounted Controls (see Fig. 3.4) 7.

OFFSET 1

(R6) control 'is provided:to DC zero the 1st amplifier- ~

in the signal conditioning portion of the module.

8.

OFFSET 2

(R17) control is. provided" to

~ DC zero the 2nd amplifier.

in the signal conditioning portion of the module.

3.2.4 TEC Model 934 Power Bin (see Fig. 3.1).

Front Panel 1.

POWER switch turns the instrument power ON (up) and OFF (down).

2.

An indicator lamp lights when the POWER switch is energized.

3.3 S stem Pre-Operational Test and Turn-On Procedure This section details the proper procedure for initiating pre-operational RTD time response testing using the Model 1101,

1121, and 1131 LCSR Test Modules.

Prior to connecting any test equipment to the plant RTD, the I

following checks,

tests, and measurements must be performed.

An oscilloscope, DVH, and an assortment of precision (1% or better) 100 to 500 ohm resistors are required for the performance of this procedure.

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3-10 3.3.1 Procedure.

1.

Plug all equipment into a 3 prong 120 VAC power outlet.

2.

Turn all equipment ON and allow at least 15 minutes warmup time with all switches on the Model 1121 Control Module in the standby mode as follows:

TEST DISABLE BRIDGE CtGUKNT + OFF-MODE-AUTO MANUAL DISABLE OFF MANUAL 3.

Switch the DVM to the resistance measurement mode and verify operability via the assorted precision resistor set.

4.

Using the same DVM, determine and label the input/output leads of the RTD to be tested and record RTD information on a data sheet that includes the following information:

Mfr:

Serial No.:

Model No.:

Resistance:

ohms 5 ~

From vendor specifications, determine the maximum permissible step current IRTD, for the RTD to be tested.

Record that information on the data sheet.

6.

On the Model 1131 Current Module, turn CURRENT ADJUST CCV to 'zero.

7.

Connect a precision test resistor that is about the same as the RTD resistance to the Amphenol connector interface cable per Fig. 3.5 Amphenol Connector

. RED WHITE PRECISION TEST BLACK RESISTOR SHIELD Figure 3.5 Test Setup Using Precision Resistor.

7

4 3-11 8.

Connect the interface cable to the'TEST RTD input on the Model I

1101 LCSR Bridge/Amplifier Module.

9.

Switch the DVM to the current measurement mode and connect test leads to the appropriate test jacks on the Model 1131 Constant Current Module.

While observing the DVM, rotate the CURRENT ADJUST knob CW until the current reaches a value of 2 IRTD.

Note:

The TEST/DISABLE switch on the 1121 Control Module II must be in the DISABLE position.

[Steps 10 through ll establish the lower current level of the LCSR test steps.]

10.

On the Model 934 Power Bin,.turn. the POWER OFF.:

Remove the Model 1121 Control 'Module from the power bin and select the desired lower current level using the PC board mounted switch provided.

Table 3.1 provides information necessary to set the four section PC mounted BRIDGE CURRENT DIVIDER switch (Sl-4).

As seen from the look-up table, the RTD resistance (at the operating tamperature) is given across the top of the table in 25 ohm increments up to 550 ohms.

Switch settings are given in the left four vertical columns (a 1 meaning the switch is ON, 0

meaning OFF).

Record the lower current level setting in mA on the data sheet. and in step 4.

11.

Replace the Model 1121 Control Module and turn the POWER ON.

[Steps. 12 through 14 set the level of the recorded test sync pulse utilized during subsequent computer based analysis of LCSR data.]

12.

Place the BRIDGE CURRENT + OFF switch on the 1121 Control Module to OFF; the MODE AUTO MANUAL switch to MANUAL; the TEST DISABLE switch to TEST.

TABLE 3.1 BRIDGE CURRENT DIVIDER SWITCH SETTINGS RTD Resistance Sl S2 S3 S4 100 125 150 175.200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 High to Low Current Ratio 0

0 0

0 1

0 0

0 0

1 0

0 1

1 0

0 0

0 1

0 1

0 1

0 0

1 1

0 1

1 1

0 0

0 0

1 1

0 0

1 0

1 0

1 1

1 0

1 0

0 1

1 1

0 1

1 0

1 1

1 1

1 1

1 3

3 4

4 4

4 4

5 5

5 5

5 6

6 6

6 7

7 7

8 7

8

.8 8

9 8

9 9

10 10 9

10 10 11 11 10 11 11 12 13 ll 12 13 13 14 12 13 14 14 15 13 14 15 16 16 14 15 16 17 18 15 16 17 18 19 16 17 18 19 20 17 18 19 20 21 18 19 20 21 23 4

4 4

5 5

5 6

6 6

6 7

7 7

8 8

8 8

9 9

9 9

10 10 11 11 ll ll 12 12 12 12 12 13 14 14 13 14 14 15 16 15 15 16 '7 17 16 17 17 18 19 17 18 19 20 20 18 19 20 21 22 20 21 22 23 23 21 22 23 24 25 22 23 24 26 27 24 25 26 27 28 5

5 6

7 8

8 10 10 ll 12 13 13 15 15 16 17 18 19 19 20 21 22 23 24 24 25 26 27 28 29 29 30 5

5 7

7 9

9 10 ll 12 13 14 14 16 16 17 18 19 20 21 22 23 23 24 25 26 '7 28 29 30 31 31 33 6

6 6

6 7

8 8

8 9

10 10 10 ll ll 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 23 22 23 24 25 24 25 26 27 26 27 28 29 28 29 30 31 30 31 32 33 32 33 34 35 34 35 36 37 6

,8 10 13 15 17 19 21 23 25 27 30 32 34 36 38

3-13 13.

While observing the 'output from the PULSE OUTPUT jack on the Model 1121 Control Module (oscilloscope),

adjust the PULSE HEIGHT control for the desired dc level.

14.

Return the TEST DISABLE switch on the Model 1121 Control Module to the DISABLE position.

[Steps 15 through 23 outline procedures necessary to operate the Model 1100 series modules in the MANUAL test mode.]

15.

On the Model 1121 Control Module, place AUTO MANUAL MODE switch in MEAL position.

16.

On the Model 1101 LCSR Bridge/Amplifier Module,- place the Gain

.switch to 20.

17.

While monitoring the output (with oscilloscope and/or DVM) from the LCSR OUTPUT jack on the Model 1101 LCSR Bridge/Amplifier Module adjust the OFFSET trim pot for zero volts.

18.

On the Model 1101 LCSR.Bridge/Amplifier Module, set the FINE BALANCE control to 10.0 (or CW full scale) 19.

On the Model 1121 Control Module, place the BRIDGE CURRENT + OFF-switch to the desired current polarity position.

20.

While monitoring the output (DVM) from the LCSR OUTPUT jack on the Model 1101 LSCR Bridge/Amplifier Module, rotate the COARSE BALANCE switch clockwise until the polarity of the output crosses the zero reference.

21.

On the Model LCSR 1101 Bridge/Amplifier Module, rotate the FINE BALANCE control CCW until the'utput noted in step 20 is zero volts.

3-14

[The LCSR modules are now properly calibrated and adjusted to perform a LCSR measurement on a single RTD in eith'er the liANUAL or AUTO Mode.

When it is desired to test a similar RTD, it will not be necessary to repeat this pre-operational test.]

22.

While observing the LCSR OUTPUT on an oscilloscope, place the TEST DISABLE switch on the Model 1121 Control Module in the TEST position.

Ver'ify that a proper LCSR output waveform is present each time this switch is placed from the DISABLE to TEST position.

[Steps 23 through 25 outline operation of the LCSR instrumentation in the AUTO mode of operation.]

23.

To operate the LCSR instrumentation in the AUTO MODE, a function generator capable of producing 5 V 8 10 ma must be used.

The repetition rate will be dependent upon the sensor under test.

24.

Connect the function generator output to the AUTO STEP INPUT jack on the Model 1121 Control Module.

25.

Place the AUTO MANUAL MODE switch on the Model 1121 Control Module in the AUTO position and repeat step 22..

26.

Re-establish all switch settings per step 2 and remove the precision test resistor installed in step 7 from the Amphenol connector interface.

The LCSR instrumentation is now ready for testing of plant RTDs as outlined in Sect.

3.4.

3.4 RTD Testin Procedure Utilizin the Model 1100 Series LCSR Instrumentation This section details the proper procedure for initiating RTD time response testing using the Model 1100 Series LCSR Instrumentation assuming the results are to be recorded for off-line analysis.

These procedures would be adjusted only slightly for on-line analysis.

Appropriate plant approvals must be granted prior to connecting any test equipment to the plant RTDs or

3-15 associated instrumentation..

Pre-operational tests on the LCSR instrumentation shall have been performed per Sect.

3.3.

..A calibrated FM tape recorder with at least two operable channels will be available for recording the LCSR data.

A functional test consisting of simultaneously recording foi a minimum'of one minute (on each channel to be used) 1V RMS sine waves at frequencies of 1,

10,

100, and 1000 Hz is recommended.

The recorded test signals should be played back to verify proper, frequency and amplitude response prior to initiating the LCSR test.

3.4.1 Procedure.

1.

Perform steps 1 through 22 and 26 from the pre-operational procedures (Sect. 3.3.1).

2.

Connect the LCSR Instrumentation Outputs (LCSR OUTPUT, and PULSE OUTPUT) to two channels of the FH tape recorder that has been calibrated.

Record applicable tape speed (15/16 Intermediate Band is normally sufficient) information on the:-

LCSR Data Sheet.

See sample sheet on. Fig. 3.6.

3.

Tee into the appropriate input line to the tape recorder and observe the output signal from the Model 1101:.LCSR Bridge/

Amplifier Nodule (oscilloscope, and D&) before,

during, and after the test to verify proper LCSR response, and that the module is properly zeroed.

4.

Instruct plant personnel to disconnect RTD from plant instrumen-tation so that no plant instrumentation wiring (other than extension leads to RTD under test) comes in contact with LCSR test instrumentation.'

3-16 RTD LCSR TEST DATA SHEET (SAMPLE)

DATE:

LOCATION:

TIME:

RTD MFR.:

MODEL NO.:

SERIAL NO.:

NOMINAL RESISTANCE:

Step 5

Measured resistance data Operating Temperature:

Element Resistance:

oF ohms 8

'F Loop Resistance (1, 3):

Loop Resistance (2, 3):

Loop Resistance (1, 2):

Remarks:

ohms ohms ohms Step 7

Data Acquisition Date Tape No.:

Tape Speed

ips, IB Tape Counter Reading (Start):

Tape Counter Reading (Stop):

LCSR Data Channel No.:

Sync Pulse Data Channel No.:

Signature Figure 3. 6 Sample LCSR Data Sheet.

3-17 5.

Measure and record all applicable resistance data concerning the RTD under test on the LCSR Data Sheet.

Note:

During these measurements a

VOM should be used and the behavior of the RTD under test noted.

For absolute resistance measurements, a

DVM should be used.

6.

Connect the RTD under test to the LCSR instrumentation test cables per Fig. 3.7 "and verify connections.

Amphenol Connecto

~'ED WHITE TEST RTD SHIELD Figure 3.7 RTD Test Connections.

7.

Record tape footage counter reading from tape recorder on attached data sheet and start recorder at least 10 seconds before stepping the current to the RTD.

8.

Step the current to the RTD under test by placing TEST DISABLE switch in the TEST position and leave it in that position for a time > 4v (estimated) before returning to the DISABLE position.

9.

Leave the TEST DISABLE switch in the DISABLE position for a time equal to or greater than the test time before returning to the TEST. position.

10.

Repeat steps 8 and 9 until the desired number of LCSR steps (we recommend P 10) have been performed.

a See Sect.

3.3, steps 23 through 25 for AUTO Mode operation.

1