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minals and the wires from the other pair to the black terminals. If there is a
shield or guard wire connect it to the green terminal.
7.3.2
Setting Coefficients
Once a PRT or SPRT probe is properly connected to the 2560/2567, the 1560
can read its resistance. To display temperature accurately, the 1560 must be
programmed with the characterization coefficients for the sensor. This is done
using the EDIT PROBE soft-key in the PROBE menu (see Section 5.2.1). The
coefficient values are normally provided with the probe on a calibration report.
Be sure to select the proper range for ITS-90 characterizations. If IEC-751
RTDs are used you may select the CVD conversion and use R0: 100, ALPHA:
0.00385, DELTA: 1.507, and BETA: 0.111.
7.3.3
Current
The 2560/2567 sources current to the sensor and measures the resulting voltage
across the sensor to determine its resistance. The current alternates every 0.5
seconds to reduce the effects of thermoelectric offsets. The normal current is
1.0 mA (2560) or 0.1 mA (2567). The current can be changed to test self-heat-
ing effects using the SET UP DEVICE function in the MODULE menu (see
Section 5.4.2). Change the CURRENT parameter and press ENTER.
The SET UP DEVICE function also allows access to two other parameters.
SAMP PER selects the sample period between 2 (normal) and 10 seconds. RES
RANGE sets the resistance range between AUTO ranging (normal), LOW
range, and HIGH range. The purpose of these options is mainly for trouble-
shooting and they should not be changed during normal operation.
7.3.4
Device Setup Commands
The SYST:MODn:DEVn:READ? and SYST:MODn:DEVn:WRIT commands
(see Sections 6.5.8.19 and 6.5.8.20) can be used to read or set the setup param-
eters for the 2560/2567 SPRT Module. The device number of the SPRT Input
Device is 1. The module number for the 2560/2567 module is its position in the
stack. For example, if the 1560 has four add-on modules, the 2560/2567 being
first, the module number for the 2560/2567 is 1. Table 23 shows the device
commands used to read or set the setup parameters of the SPRT Input Device.
Table 23 SPRT Module Device Commands
Device Command
Parameter
CURR
1, 1.4 (2560)
0.1, 0.05 (2567)
SAMP
2, 10
ARNG
AUTO, LOW, HIGH
7 2560/2567 SPRT Module
Description
Excitation current, mA
Sample period, seconds
Resistance range
Operation
115
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