DI-245 THERMOCOUPLE ISSUES

DI-245 THERMOCOUPLE ISSUES

We purchased a DI-245 a while back and have finally began using it. We coupled it with Type J thermocouples from thermetrics and installed the Dataq software. An ice slurry to calibrate and we’re ready to go. All 4 sensors read the ambient temps correctly however once placed in a refrigerated test case (running between 29-38°f) the readings are roughly 18°f lower as compared with a several hand held digital thermometers. Can you offer any suggestions?