OMEGA Engineering, Inc. 4-Channel RTD Input Data Acquisition Module PT-104A

The PT-104A is a four-channel, high-resolution temperature data acquisition module for use with PT100 and PT1000 RTD sensors. It can also be used to measure resistance (375 ω and 10,000 ω ranges) and voltage (115 mV or 2.5 V ranges). In PT100/PT1000/ resistance mode, the unit uses a four wire circuit. In voltage mode, the input connector can be treated as a differential input with ground, or two single-ended inputs. Both inputs must be 0V or above, though it does not matter which input has the higher voltage. For the 115 mV voltage range, the accuracy may vary by 2%, and the temperature coefficient will be 100 ppm/°C. Although accurate temperature sensors are widely available, it has been difficult to take advantage of them due to errors caused by the measuring device. The PT-104A, however, is designed to be inherently accurate. Rather than relying on voltage references (which tend to be temperature sensitive) it uses ‘reference’ resistors which are extremely stable (low temperature coefficient and drift). The exact value of each resistor is stored in an EEPROM to provide the ultimate in accuracy (yearly re-calibration is recommended). To achieve the 0.001°C resolution a highlyadvanced ADC is used that can resolve to better than 1 part in 16 million.