The IS200VRTDH1BBA model is a Resistance Temperature I/O Processing Device. This model can be used with a DRTD DIN Euro Size Terminal Board. When the VRTD model is running it can accept up to sixteen three-wire resistance temperature device (RTD) inputs. The VRTD board can convert the potential inputs into digital temperature values when these inputs have been converted it will transmit them over to the VME backplane to the VCMI, and finally to the controller.
One feature of the IS200VRTDH1BBA board is the VCO-type A/D converter. The converter will use voltage-to-frequency converters as well as sampling counters. There are both signals and excitation currents that are sampled from the converter which will be four times per second more for normal mode scanning with twenty-five times per second for fast mode scanning by using a time sample interval that is related to the power system frequency.
On the front panel of the VRTD board, there are three LEDs located at the top of the board. These LEDs are used to provide status information. The main LEDs indicate the RUN and FAIL conditions, the FAIL LED will be solid red with the RUN LED flashing green. The third LED is typically off but if a diagnostic alarm condition occurs on the board it will be a steady orange.
This model can also be used with a TRTD board. The TRTD board has a feature that can ensure that the RTDs on the TRTD board are not excited by two of the potential VRTD boards at the same time which could possibly produce bad readings. All of the above information can be found in the GEH-6421C Mark VI Volume II System Guide.