This page displays additional configuration parameters for analog/universal inputs. Each input may be enabled as an analog input, fast 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.

Analog inputs use 15-bit sigma-delta conversion by default with a total 18-channel scan time of approximately 7 seconds. Noise rejection is highest in this mode. Fast analog is a 10-bit conversion and all channels are scanned several times a second in fast mode. Discrete application of the analog/universal input automatically uses fast conversion. Thermistor linearization is only available to high resolution analog mode. Unused inputs should be set to discrete or fast analog modes to allow faster scan time for the used inputs.

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.

The Threshold/Filter field becomes a filter enable flag when the input is set to Fast analog. If the filter enable is set to zero, raw data will be saved without filtering. If the filter enable is set to 1 (any non-zero value), a sliding window of sixteen fast samples will be averaged to produce a reading.

Slope and intercept are used to scale raw binary data to floating point engineering units. Raw binary data will be scaled and stored in the input's analog input object. Normally the actual analog data will be scaled; however, if the input type is discrete, the values of 0 and 1 are used as the on/off input data and this value is reflected by the respective binary input object.

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.

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.

All configuration options are available for inputs 1 through 16. Inputs 17 and 18 may only be analog (0-10V) with slope and intercept applied.