Commissioning Ceraphant PTP31B, PTP33B
32 Endress+Hauser
8.6 Configuring process monitoring
To monitor the process, it is possible to specify a pressure range which is monitored by the
limit switch. Depending on the device version, the process can be monitored using one PNP
switch output, or optionally using a second PNP switch output or an analog 4 to 20 mA
output. Both monitoring versions are described below. The monitoring function allows the
user to define optimum ranges for the process (with high yields etc.) and deploy limit
switches to monitor the ranges.
8.6.1 Digital process monitoring (switch output)
It is possible to select defined switch points and switchback points which act as NO or NC
contacts depending on whether a window function or hysteresis function is configured
→ 32.
Function Output Abbreviation for operation
Hysteresis Closing HNO
Hysteresis NC contact HNC
Window Closing FNO
Window NC contact FNC
If the device is restarted within the specified hysteresis, both switch outputs are open (0 V
present at the output).
8.6.2 Analog process monitoring (4 to 20 mA output)
• The 3.8 to 20.5 mA signal range is controlled according to NAMUR NE 43.
• The alarm current and current simulation are exceptions:
– If the defined limit is exceeded, the device continues measuring in a linear fashion.
The output current increases linearly up to 20.5 mA and holds the value until the
measured value drops below 20.5 mA again or the device detects an error .
– If the defined limit is undershot, the device continues measuring in a linear fashion.
The output current decreases linearly to 3.8 mA and holds the value until the
measured value rises above 3.8 mA again or the device detects an error .
8.7 Functions of switch output
The switch output can be used for two-point control (hysteresis) or for monitoring a
process pressure range (window function).
8.7.1 Hysteresis
SP1/SP2 switch point value, output 1/2
RP1/RP2 switchback point value, output 1/2
Navigation SP1/SP2
RP1/RP2
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