This page displays additional configuration parameters for analog/universal inputs. Each input may be enabled as an analog input, discrete, or dry contact input. If an analog input type is selected, the input scaling should also be selected as 0-10V or one of the thermistor types. If a discrete input type is selected, the logic sense (normal or inverted) should be selected from the scaling list.

Threshold is a percentage (0-100%) of full scale that should be treated as the on/off threshold when the universal input is set to Discrete input type. The input will be regarded as "on" when the input goes above this level. The input will return to the "off" state when the input drops to this level minus 6% hysteresis.

Important note about invert/normal scaling of discrete or dry contact input: When input type is discrete, the input expects an externally sourced voltage signal, and the input will be "on" when the voltage is above the threshold. When dry contact is selected, excitation of the input is provided internally. An open input will therefore produce a full scale reading, or "on" state. A contact closure to ground will produce an "off" state. If it is desired that the closed contact should produce an "on" value, then "Inverted" should be selected for the dry contact input.

Slope and intercept are used to scale raw binary data to floating point engineering units. Raw binary data will be stored in the integer register associated with the input while scaled data will be stored in the input's floating point register. Normally the actual analog data will be scaled; however, if the input type is discrete, the values of 0 and 10.0 are used as the on/off input data and slope/intercept are applied to those values.

Additional scaling is done internally if any of the thermistor scaling types are selected. These are for 3k, 10k, or 20k thermistor inputs, types II, III, or IV as specified for Precon brand thermistors. These curves are very similar to, if not identical to, curves for other brands. These are linearized to degrees F or C and provided in hundredths of degrees. Integer values are scaled x100, thus an integer register value of 7200 means 72.0 degrees. (Integer registers do not reflect raw binary data when thermistor scaling is selected.)

Internal thermistor scaling is done before slope and intercept are applied. Normally slope=1.0, intercept=0.0 for thermistor inputs. If you wish to correct sensor offset, you can use slope/intercept to do this correction.