A33920 — Encoder 3: Temperature sensor fault

A33920 is raised by the Sensor Module Encoder 3 when the motor temperature sensor connected to it cannot be evaluated: the measured resistance lies outside the range the module expects for the selected sensor type. The manuals print the condition as an alarm; depending on the drive's configuration the same condition can also be output as a fault or as a message without a response. On S120 and S150 the manual titles it Encoder 3: Temperature sensor fault (motor). The condition does not make the drive trip — it only reports the sensor problem.

• An error occurred while the module was evaluating the temperature sensor. Two fault causes are distinguished: a wire breakage or a sensor that is not connected, and a measured resistance that is too low for the selected sensor type (PTC, KTY or PT1000).
• Which of the two applies is coded in the message value; the manuals also print additional values that are only for internal Siemens troubleshooting.

1. Check that the encoder cable is the correct type and is correctly connected.
2. Check the temperature sensor selection in p0600 to p0603.
3. If the cable and the sensor selection are in order, replace the Sensor Module — the manual names a hardware defect or incorrect calibration data as the remaining reasons.

• The message value carries two items: the fault cause (%1) and the channel number (%2).
• In r0949 or r2124 the information is coded as 0000yyxx hex: yy = channel number, xx = error cause.
• Error cause 1 (= 01 hex): wire breakage or sensor not connected — KTY: R > 1630 Ohm, PT1000: R > 1720 Ohm.
• Error cause 2 (= 02 hex): measured resistance too low — PTC: R < 20 Ohm, KTY: R < 50 Ohm, PT1000: R < 603 Ohm.
• Additional values: only for internal Siemens troubleshooting.

• r0949 (fault value): holds the coded message value when the condition is stored as a fault — fault cause and channel number in the 0000yyxx hex pattern described above.
• r2124 (alarm value): the same readout while the condition is active as alarm A33920.
• p0600 (motor temperature sensor for monitoring): check that the sensor type actually connected to Encoder 3 is the one selected here.
• p0603 (CI: motor temperature signal source): check which signal source is interconnected as the motor temperature for this encoder.

As an alarm, A33920 requires no acknowledgement: it is present only while the sensor signal is outside the permissible range and disappears once the signal is back to normal. The drive is not switched off by the condition itself. Where the configuration issues the same condition as a fault, it can be acknowledged right away — without a power-up cycle or waiting period — and the drive can run again as soon as the cause (cable, sensor selection or Sensor Module) has been remedied.