Spectrum-controls 1769sc-IF8u Manuel d'utilisateur télécharger pdf (Page 40)

30 Compact IO

™

Universal Input module

NOTE: When using an ungrounded thermocouple, the shield must be

connected to ground at the module end.

IMPORTANT: When using grounded and/or exposed thermocouples

that are touching electrically conductive material, the ground potential

between any two channels cannot exceed ±10V dc, or temperature readings

will be inaccurate.

Cold Junction

Compensation

To obtain accurate readings from channels configured for

thermocouple, the cold junction temperature (temperature at the

module’s terminal junction between the thermocouple wire and the

input channel) must be compensated. One cold junction compensating

thermistor has been integrated into the removable terminal block. This

thermistor must remain installed to retain accuracy. If the thermistor

assembly is accidentally removed, re-install it by connecting it across

the CJC terminals.

Note: Thermocouple accuracy can differ between channels on the

terminal block. Channels that are physically located further from the

CJC sensor are more likely to exhibit a temperature offset. The figure

below shows the CJC accuracy for each channel.

Note: Using a remote terminal block can improve CJC accuracy.

When using remote terminal blocks, remove the CJC sensor from the

module RTB and mount it on the remote terminal block. Be sure to

use shielded twisted pair wire between the module and the remote

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Spectrum-controls 1769sc-IF8u Manuel d'utilisateur Page 40