Measurement Computing TempScan/1100 - Manual (Page 51)

TempScan / MultiScan User's Manual 889897 Scanning Cards 3-3
Fault Detection: Open thermocouple may be detected by a software query.
Cold Junction Sensors: One for every 8 input channels.
Linearization: Performed by lookup table (varies by T/C type); table supports two user-defined custom
T/C types of up to 256 points each. Lookup tables are stored in battery backed-up NV-RAM.
Input Impedance: 1 MOhm typical
Input Bias Current: 20 nA maximum.
Maximum Allowable Input:
± 35V peak.
Channel to Digital Low Isolation: For standard: 500V maximum; For CE: 200V maximum.
Channel to Channel Isolation:
± 10V peak.
Temperature Coefficient: 0.03 °C/°C.
Digital Filtering: Averages 16 samples @ 50/60 Hz for line cycle noise rejection.
Voltage Range, Accuracy and Resolution: 100 mV;
± 0.02%; and 3.05 µV.
Voltage Units: Volts, counts.
TempTC/32B Description
The TempTC/32B thermocouple scanning card contains 32 differential input channels, each of which may
be configured as any thermocouple type or as a millivolt input. Temperature values may be returned in
units of °C, °F, °K, °R, or mV.
There is a 4700-picofarad polypropylene capacitor connected across the input terminals of each channel.
This capacitor acts to filter some of the input noise when measuring thermocouples. When the circuit card
is set to the ±100 millivolt range, this capacitor will react with the user source impedance to form a low-
pass filter. The filter pole frequency will be 1/(2*pi*(RSHI + RSLO)*4700 * 10
-12 ), where RSHI and RSLO
are the source resistance of the input leads.
When making differential voltage measurements with the TempTC/32B card, you should insure that one of
the common terminal blocks is connected to the common of the unit being measured.