Campbell Scientific CR9000X Measurement and Control System - Manual (Page 316)

Section 8. Processing and Math Instructions
To achieve the highest accuracy it is usually best to calibrate
individual sensors over the range of use and apply corrections to
the
R
S
/R
0
value input to the instruction (by using the calibrated
value of R
0
) and the multiplier and offset parameters of PRTCalc.
NOTE
Parameter
& Data Type Enter PRTCALC PARAMETERS
Dest
Var. or Array
The variable in which to store the temperature in degrees C.
Reps
Constant
The number of values to determine. When repetitions are greater than 1, the source must be an array..
Source
Variable
The name of the Variable that is the input for the instruction. Must be the ratio R
S
/R
0
, where R
S
is the
RTD resistance and R
0
the resistance of the RTD at 0 ° C.
PRTType A code to select the PRT Standard to use
Constant Code Description
0 DIN 43760 specification adjusted (1980) to the International Electrotechnical Commission
standard. Same as original PRT instruction.
1 IEC 60751:2008 (formally known as IEC 751), alpha = 0.00385. Now internationally adopted
and written into national standards, e.g. ASTM E1137-04, JIS 1604:1997, EN 60751 and
others. This should be used with any probes claiming compliance with those or older standards
where the probe has alpha = 0.00385, e.g. DIN43760, BS1904
2 US Industrial Standard, alpha = 0.00392
3 US Industrial Standard, alpha = 0.00391
4 Old Japanese Standard JIS C 1604:1981, alpha = 0.003916
5 Honeywell Industrial Sensors, alpha = 0.00375
6 ITS-90 SPRT, alpha = 0.003926
Mult, Offset
Constant,
Variable,
Array, or
Expression
A multiplier and offset by which to scale the raw results of the measurement. See the measurement
description for the units of the raw result; a multiplier of one and an offset of 0 are necessary to output in
the raw units. For example, the TCDiff instruction measures a thermocouple and outputs temperature in
degrees C. A multiplier of 1.8 and an offset of 32 will convert the temperature to degrees F.
Randomize(Source)
Initializes the random-number generator.
Syntax
Randomize [number]
Remarks
The argument number can be any valid numeric expression. Number is used to
initialize the random-number generator by giving it a new seed value.
If Randomize is not used, the RND function returns the same sequence of random
numbers every time the program is run. To have the sequence of random numbers
change each time the program is run, place a Randomize statement with no
argument at the beginning of the program. See RND instruction's example program.
8-30