Campbell Scientific CR9000X Measurement and Control System - Manual (Page 241)

Section 7. Measurement Instructions
7-17
Parameter
Enter AM25T PARAMETERS
TRef
Variable
The variable whose value is used for the reference temperature for the thermocouple measurements. If
the ExChan parameter is set to set to non-zero, the measured value of the PRT will be loaded into this
variable. If EXChan is set to 0, the current TRef value will be used as the reference temperature.
ExCardSlot
Constant
The number of the slot that contains the CR9060 Module used to Clock and Reset the multiplexer and to
provide excitation for the reference temperature PRT.
ClkPort
Constant
The Digital Output port number on the CR9060 Module that will be used to clock the AM25T. One
clock port may be used with several AM25Ts.
ResPort
Constant
The Digital Output port number on the CR9060 Module that will be used to enable and reset the
AM25T. Each AM25T must have it's own unique Reset line.
ExChan
Constant
The Excitation Channel number on the CR9060 Module that will be used to provide excitation for the
PRT reference temperature measurement. If 0 is entered, the PRT is not measured.
RevDiff
Constant
Option to reverse inputs to cancel offsets. This technique cancels voltage offsets in the measurement
circuitry but requires twice as much time to complete the measurement.
Value
0 Inputs are not reversed.
1 A second measurement is made after reversing the inputs
SettlingTime
Constant
The time in microseconds to delay between setting up a measurement (switching to the channel, setting
the excitation) and making the measurement (10 microsecond resolution).
The minimum recommended Delay for AM25T measurements is 70 µS.
Entry Voltage
Range
Delay CR9055
Voltage Range
Delay
0 ± 50 mV 20 µS (default) ± 0.5V 40 µS (default)
0 ± 200 mV 20 µS (default) ± 2 V 40 µS (default)
0 ± 1000 mV 10 µS (default) ± 10 V 30 µS (default)
0 ± 5000 mV 10 µS (default) ± 50 V 30 µS (default)
> 0 all Truncate to closest 10 µS all Truncate to closest 10 µS
Integ
Constant
The integration time in microseconds for each of the channels measured (10 microseconds resolution).
The minimum recommended Integration time for AM25T measurements is 70 µS.
Mult, Offset
Constant, Var,
Array,Express.
A multiplier and offset by which to scale the raw results of the measurement. 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.
R*: Place an R at the end of the range code (ex: 50mVCR) in order to perform an Input Voltage Limit check
before making the measurement.
See Section 3.1.2 SE and Diff. Voltage Measurements for details on the R,
Input Limit check, option.
This instruction cannot be used in a SubScan or in a
SlowSequence Scan.
'This example demonstrates using the AM25T thermocouple multiplexer with the CR9000X.
'\\\\\\\\\\ VARIABLES and CONSTANTS //////////
Const AM25TChan = 1 'starting channel in AM25T
Const ESlot = 6 '9060 module slot
Const Clk = 1 '9060 Digital Control Output port
Const Res = 2 '9060 Digital Control Output port
Const EChan = 10 '9060 Excitation Channel
Const Integ = 500 'integration time in uSecs of each AM25T measurements
Public RefT, Mux(25)
DataTable(MUXTC, 1, 2000)
Sample(MuxReps,Mux(),FP2)
EndTable
BeginProg
Scan (200, mSec, 0, 0)
AM25T (Mux(), 25, mV50, 1, 5, 14, TypeT, RefT, ESlot, , Clk, Res, EChan, 0, 140,70 , 1, 0)
CallTable MUXTC
NextScan
EndProg
NOTE