Campbell CR850, Operator'S Manual

Page: 254 / 566

Section 7. Installation
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'Declare Event Driven Data Table
DataTable (Event,True,1000)
DataEvent (0,DeltaT_C>=3,DeltaT_C<3,0)
Sample (1,PTemp_C, FP2)
Sample (1,AirTemp_C, FP2)
Sample (1,DeltaT_C, FP2)
EndTable
'Declare Time Driven Data Table
DataTable (OneMin,True,-1)
DataInterval (0,1,Min,10)
Sample (1,EventCounter, FP2)
EndTable
BeginProg
Scan (1,Sec,1,0)
'Wiring Panel Temperature
PanelTemp (PTemp_C,_60Hz)
'Type T Thermocouple measurements:
TCDiff (AirTemp_C,1,mV2_5C,1,TypeT,PTemp_C,True,0,_60Hz,1,0)
'Calculate the difference between air and panel temps
DeltaT_C = AirTemp_C - PTemp_C
'Update Event Counter (uses special syntax Event.EventCount(1,1))
EventCounter = Event.EventCount(1,1)
'Call data table(s)
CallTable (Event)
CallTable (OneMin)
NextScan
EndProg
7.8.18 PRT Measurement
PRTs (platinum resistance thermometers) are high-accuracy resistive devices used
in measuring temperature.
7.8.18.1 PRT Calculation Standards
Two CR800 instructions are provided to facilitate PRT measurement.
PRT() : an obsolete instruction. It calculates temperature from RTD
resistance using DIN standard 43760. It is superseded in probably all
cases by PRTCalc() .
PRTCalc() : calculates temperature from RTD resistance according to one
of several supported standards. PRTCalc() supersedes PRT() in probably
all cases.
For industrial grade RTDs, the relationship between temperature and resistance is
characterized by the Callendar-Van Dusen (CVD) equation. Coefficients for
different sensor types are given in published standards or by the manufacturers for