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The SIM922 Diode Temperature Monitor and the SIM923 Platinum RTD
Monitor are designed to measure four sensors simultaneously. Based
on the modular SIM platform, they provide high-performance and multiple-channel
capability in a small footprint.
SIM922
Each of the four channels in the SIM922 has an independent, precision
10 µA current source to provide sensor excitation. Measurement
results can be displayed in either kelvin or volts.
SIM923
The four channels in the SIM923 have independent, stable 1 mA current
sources to provide sensor excitation. Sensor resistance is determined
ratiometrically with a half-bridge circuit consisting of the sensor
and an internal reference resistor. The current to the sensor can
be reversed by the user to test for any offset. Measurement
results can be displayed in either kelvin or ohms.
Common Features
Both the SIM922 and SIM923 employ four-wire measurement circuits
(±I excitation leads, ±V sense leads) making the measurements
insensitive to series lead resistance. The four channel excitations
are independently controlled and do not switch on or off when the
readout is advancing between channels. Sensor excitations can be
disabled to reduce power dissipation at sensitive cryogenic stages.
This also accelerates readings in the remaining enabled channels.
Measurements are performed at rates up to four readings per second.
A factory-standard calibration curve is built in for each model.
In addition, each channel has non-volatile memory to store a 256-point
custom calibration curve to convert sensor units (V or Ω
) to temperature units (K). Results are displayed on easy to read
4-digit LED displays. Full remote operation is available over the
serial interface.
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