Analog output overrange examples - HPP271

HPP271 User Guide

Document code
M211888EN
Revision
E
Language
English
Product
HPP271
Document type
User guide

Consider a probe with one of the analog output channels (4 ... 20 mA) configured to output H2O2 concentration, scaled to 0 ... 2000 ppm.

Example: Clip the high end of the output at 2100 ppm, and enter the error state at 2200 ppm

Configure the high-end clipping limit and error limit as follows:

  • Clipping limit, high end: 5 % of scale (= 2100 ppm, clipped at 20.8 mA)
  • Error limit, high end: 10 % of scale (= 2200 ppm)

When the measured H2O2 concentration rises above 2000 ppm, the output rises above 20 mA. The output keeps rising until the measurement is 2100 ppm, at which point the probe outputs 20.8 mA. If the H2O2 concentration rises above 2100 ppm, the output still remains at 20.8 mA. If the H2O2 concentration rises above 2200 ppm, the output enters the error state (by default, 3.6 mA).

Figure 1. Analog output overrange example with clipping and error limits

Example: Clip the high end of the output at 2100 ppm, but do not enter the error state at all

Configure the high-end clipping limit and error limit as follows:

  • Clipping limit, high end: 5 % of scale (= 2100 ppm, clipped at 20.8 mA)
  • Error limit, high end: empty (or in Modbus: "NaN")

When the measured H2O2 concentration rises above 2000 ppm, the output rises above 20 mA. The output keeps rising until the measurement is 2100 ppm, at which point the probe outputs 20.8 mA. If the H2O2 concentration rises above 2100 ppm, the output still remains at 20.8 mA.

Figure 2. Analog output overrange example with clipping only

Example: Do not clip the output at all, but enter the error state at 2200 ppm

Configure the high-end clipping limit and error limit as follows:

  • Clipping limit, high end: empty (or in Modbus: "NaN")
  • Error limit, high end: 10 % of scale (= 2200 ppm, 21.6 mA)

When the measured H2O2 concentration rises above 2000 ppm, the output rises above 20 mA. The output keeps rising until the measurement exceeds 2200 ppm (21.6 mA), at which point the output enters the error state (by default, 3.6 mA).

Figure 3. Analog output overrange example with no clipping, only error state when error limit is exceeded