ML19262A145
| ML19262A145 | |
| Person / Time | |
|---|---|
| Issue date: | 10/05/1979 |
| From: | Jaske R NRC OFFICE OF STATE PROGRAMS (OSP) |
| To: | Grimes B Office of Nuclear Reactor Regulation |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 NUDOCS 7910260433 | |
| Download: ML19262A145 (8) | |
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NUCLEAR REGULATORY COMMISSION _ M f?
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CT 5 79,g hk MEMORANDUM FOR:
Brian K. Grimes, Assistant Director for Engineering and Projects, NRR FROM:
Robert T. Jaske, SP
SUBJECT:
METEOROLOGICAL TOWER DATA TRANSMISSION LINKAGE Recently we' talked about the nature of measurements which might be covered by Reg Guide 1.97, in order to better prepare for the use of computer assisted emergency management.
One key elemen t is the ability to interrogate station meteorological data in real time.
NRR/DSE is looking into the scope and quality of.the data, and has proposed actions to improve the meteorological data base (Ref. Hulman to Weiss 10/2/79).
As an interim step, it seems wise to seek electronic coupiing of this data both for use by NRC and potentially with AMC.
Accordingly, I have asked LLL to submit a proposed standard linkage which can
. serve these two needs.
I am sending this a an enclosure.
I hope it is sufficient'to proceed with me for int fregating station data by States and NRC as part of evolving national system.
Robert T. J[ske, Technical Advisor to the Director Office op tate Programs s
Enclosure:
As Stated' 1917 207 P00R 01B M e
7910260 M
ARAC / SITE Met Interface The following specification details how meteorological measurements are to be prese'ted to the ARAC computer systems. With the diversity of meteorelogical instrumentation available, ARAC selected a 9 bit bint y format for data to transmitted from the instruments to the ARAC computer. The 9 bits are sent in two 8 bit charac ters which are transmit m.. synchronously using a Universal Asynchronous Receiver /Trans: netter (U AR/T). Binary data is multiplexed and digiti:ed from the analog sensors so that low cost, low speed transmission lines could be used. In order to verify the binary data a sirnple encription of the data is per f orm ed. The hardware necessary to perform the data conversion is described in section I. The software aspects of the manipulation is covered in section II.
I.
Hardware of ARAC MeteorologicalInterf ace.
The basic cornponents of the sites rneteorological interface to ARAC is shown
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in figure 1. The sensors and d/a converter are standard to most tower systems that sites may already have. The formatter is best supported with a micro-computer.
The transmitter containing a UAR/T and line drivers is the same component that would drive a teletype or some other terminal for the cornputer system. Lighting protecticn is an important part of this system and ARAC has only limited experience in this are a.
Tne modems of the figure are optional but must be supplied by the site if the tower and the ARAC co=puter are far apart.
A.
The tower, sensors, and d/a hardware are purchased by the site. The accuracy required by ARAC on all measure:nents is shown in Table 1.
Calibration can ':e perfer=ed by tae analeg.'nstruments or in software by the formatter.
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s 2-B.
The formatter c2ultiplexa the d.gitized sensor readi es into a string i
bit characters for transmission to 67 AC. "Se format of the data and order oi channels are covered in the softw. e sm aion. The formatter's. function is best described by the sof tware functions that the micro-computer woul/ erfor:n.
C.
The transmit ter should use an industry standar '
T.
This IC transmitts S bit data in an asychronous (start /stop) mode. Pari,
.ans:nission rate (baud) and stop bits at alectable by the site with the use of the U AR/T. ARAC def aults are one stop bit,1200 baud and no parity, but any ether set can be selected from Table 2.
.D.
Lightning is a common problem with meteorological towers during thunders tor =s.
Several ARAC sites have been destroyed by lightning. Suitable lightning protection must be provided to prevent damage to the ARAC system.
One method of protection is low cost microwave transmitter / receiver modules which contain a U AR/T and modem in one package.
E.
The signal recayed at the AR AC equipment can be any one of the follo4ing:,20Ma current loop, TTL, or EIA RS232C. For short distances from the transmitter to ARAC, no signal conditioning would be required; for longer distances modems may be needed and the site should select and provide the modem of its choice.
F.
ARAC provides a connector for modems (RS232C), current loop and TTL cables.
3.
So f tware The metecrological data is transmitted as records of cha.nnel readings with
- .e reccrd every 5-10 seconds. Each instru=ent er senser will be a sep arate cht....el on the =ultiplexer. There is a fer:nat to the records and a fer:2at to the channel readings. Both formats and the scaling to metric units are discussed in the folbwing sections.
s 3-A.
The record format includes a single unique synchronization charac ter followed by a pair of characters for each channel of sensor readings. The channels can be in any order that the site desires. Additional sensors beyond tne wind speed, direction and temperature measurements can be included. The synchronization
. character has all 8 bits set to a 1"
value. All other characters that are transmitted will not have the most significant binary digit set ("1").
B.
The format of the channel readings requires two characters to transmit each data reading. Nine (9) bits are required to obtain the accuracy of sensor readings as specified in Table 1. In order to transmit 9 bits in the 7 remaining bits of edch character, a specific allocation of bits to characters is defined. The 7 most significant bits (MSB) are transmitted in the first character of a channel pair. The.
Iow 2 bits (LSB) are teansmitted in the second character and are left adjusted. The MSB of each character must be "O" unless it is the synchreni:ation character, there. fore the Z LSB of the channel are left adjusted immediately to the right of the M SB. An example of the structure for each channel is shown in Figure 2. The nine bit can be manipulated to the two characters by software with Z rotates right of 16 bits (Z characters) followed by a shift right of the second character. The second chkracter can have only values of 0, 40,100, and 14C in octal expression. The format was adopted for its error detection capabilities.
C.
The u' nits of each channel reading are fixed by the following for nula:
Y = aX + b.
7 210
. X is the a/d reading and Y is the sensor reading in me' ric units. "b" is an offset to t
obta,in negative readings and "a' is a scale factor. ' Itis conversion is performed by thd ARAC syste:n, and the site provides the values for all "a's" and "b's* to adjust each channel to the range and accuracy specified in Table 1. Calibration of the instruments is a function of either the a/d unit or the formatter; local calibration is performed by the site without ARAC support.
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accuracies range Wind Direction 0.2%
O - 5400 Wind Speed 1.0%
O - 50 M/S Te mperature 0.2%
- 40^9 + 500C All values digiti:ed shall be positive, o being the smallest value, all l's being the highest. Sa:nple intervals shall be 5 to 10 seconds between readings.
Table 2
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= 110,150, 300,1200,1800, 2400 Stop
= 1,1 1/2,1 Parity
= none, odd, even, Bits
=: only 8
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