SBS IP-Thermistor 16 Channel Thermistor Temperature Reading IndustryPack

The GE Fanuc / SBS / Greenspring IP-Thermistor 16 Channel Thermistor Temperature Reading IndustryPack is a precision temperature reading IndustryPack for 16 channels of thermistor based sensors. It is a complete IP, providing a current source, multiplexers, buffers and amplifier, 12-bit analog to digital converter, factory-set offset and gain adjustment circuitry, timing and interrupt logic, and IP bus interface. IP-Thermistor is a single-high IndustryPack.

To measure temperature using a thermistor, a small stable current is passed through the sensor. Then the voltage drop is read using a buffered Analog to Digital Converter (ADC). IPThermistor uses a switched, highly stable, 1 mA current source. The current source is switched among the sixteen sensors, minimizing self-heating. The current source may be switched off to all sensors via software. A 12-bit ADC with an integral sample/hold is used to convert the voltage to a digital value. A conversion cycle takes a total of 17 µseconds. All timing, control logic, conversion and buffering is provided on the IP. When the conversion is done, the IP will either generate a programmable, vectored interrupt, or a ADC_BUSY bit may be polled by the host. The 12-bit data is signextended by the control logic to fill a 16-bit word, and may be read any number of times by the host until the next conversion has completed.

The IP-Thermistor includes a programmable 16-bit pacer clock with one µsec resolution. This clock may be programmed to start a conversion every 17 to 65,535 µsec continually. Alternatively the pacer clock may be used as a general purpose timer. The pacer clock has interrupt capability. Overvoltage protection of the IP-Thermistor's inputs is provided the multiplexers. These multiplexers can withstand up to ±35V continuous, with or without power applied. IP-Thermistor includes a calibration 2 Kbit EEPROM. Normally this EEPROM is not required; however, it is fully supported and may be used to store per-channel information by the system integrator, This is useful, for example, for holding thermistor type and calibration data that is sensor or system dependent.