Analog output overrange behavior - HPP271

HPP271 User Guide

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The analog output of the probe has a defined behavior when the values measured by the probe are outside the scaled analog output range. At first, the output is clipped when the measurement exceeds a set limit (clipping limit): the measurement continues, but the output does not change from the clipped value.

When the measurement exceeds the second limit (error limit), the analog output switches to the error state defined for the output.

The clipping and error limits are configured separately for the low and the high ends of the measurement scale. By default, the clipping limits are set to 0 %, and the error limits are set to 2 % of the scale.

You can change or disable the clipping and error limits using Vaisala Insight software or Modbus configuration registers. Changing the limits does not affect the scaling of the outputs. The definable range for each limit is 0 ... 20 %. The maximum values for limits extend the analog output range to 0.8 mA at the low end of the scale, and to 23.2 mA at the high end of the scale.

Figure 1. Maximum extensions to analog output range

The same clipping and error limits are applied when the measured value drops back to the scaled range: at first the output returns to the clipped value from the error state, and then to normal output.