BECKHOFF EL30xx Analog Input Diagnostic Guide

The 15 TxPDO toggle flips every time a new measurement value is updated and can be used to monitor the conversion cycle.

3.2 Numerical Representation (Value)

The 12 bit ADC value is left shifted by 4 bits and stored in a 16 bit signed integer (represented by the default Signed Integer). Corresponding to ± 32767 at full scale. It can also be changed to an unsigned integer or signed amplitude representation through the object 0x80n0:02.

Example: EL3002 (± 10V), when input+5V, the value is approximately 16383 (0x3FFF); When inputting -5V, the value is approximately -16384 (0xC000).

Operation mode and filter configuration

EL30xx supports three operating modes: FreeRun, Frame Triggered (SM2 synchronous), and DC mode (only available on some models). The pattern is configured through the CoE object 0x1C33:01.

4.1 FreeRun mode (default)

Filter forced on (default is 50Hz FIR notch filter).

The conversion time is fixed (approximately 0.625ms for channel 1, 1.25ms for channel 2, and longer for channel 4/8).

Asynchronous with EtherCAT cycle, updates when new data is ready, and flips TxPDO.

Applicable scenarios: Conventional data collection that requires power frequency noise suppression.

4.2 Frame Triggered Mode (SM2 Synchronous)

The filter must be turned off (0x80n0:06=0).

The terminal is synchronized with the EtherCAT cycle, and the latest measurement value is output for each cycle (provided that the cycle is not shorter than the minimum conversion time).

If the cycle is too fast, the 0x1C33:0C counter will increment, and the TxPDO toggle will not flip every cycle.

Applicable scenarios: Applications that require fast and synchronized sampling (such as aligning with motion control cycles).

4.3 Detailed Filter Settings

Filter configures all channels in the set through object 0x8000:15 (channel 1):

Value filter type characteristics

0 50 Hz FIR notch at 50Hz and harmonics, attenuation>50dB, -3dB cut-off frequency approximately 22Hz

1 60 Hz FIR notch at 60Hz, attenuation>40dB, -3dB cut-off frequency approximately 26Hz

2-9 IIR 1-8 recursive low-pass filtering, cutoff frequency reduced from 168Hz (IIR1) to 1.2Hz (IIR8)

Important restriction: Filter settings must be done through 0x8000:15, and 0x80n0:15 for other channels is invalid. The latest firmware will return an error when written incorrectly.

Common troubleshooting and diagnosis

5.1 Terminal cannot enter OP state

Possible reason: Invalid PDO configuration; Watchdog triggered; E-bus power supply is insufficient.

Solution: Check if a valid PDO combination is selected in the "Process Data" tab (if Standard and Compact are checked at the same time, it may conflict). View the 'invalid SM cfg' information in the TwinCAT log. Calculate the total current of the E-bus (typically 130mA per terminal), and if it exceeds the maximum 2A of the coupler, insert the EL9410 power supply into the terminal.

5.2 The measured value is always 0 or at full scale

Possible cause: Sensor wiring error; The sensor has no power supply; Range configuration error; Broken line.

solve:

For EL304x/EL305x single ended current input: Confirm that the 24V power supply is connected to terminal points 2/6 (+24V) and 3/7 (0V), and the sensor is connected in series between 24V and the input.

For EL301x/EL302x differential current input: Confirm sensor polarity and GND_int connection (1/2 channel terminal requires external wiring GND to stabilize common mode potential).

Check the ERROR LED: If it is lit, read the Overrange/Underrange bits of the status word. For 4-20mA terminals, a current<2mA usually triggers a disconnection.

5.3 Measurement error caused by common mode voltage (Vcm) issue

Only applicable to differential input terminals (EL301x/EL302x). The internal circuit is measured through a 33 Ω shunt resistor, and the potential difference between the midpoint of the resistor (CMP) and the internal GND must not exceed the technical specifications (usually ± 10V). If multiple channels of sensors use different power sources (such as one low side measurement and one high side measurement), the potential difference between CMPs may exceed the limit.

Solution:

For EL3011/EL3012/EL3021/EL3022: Connect terminal point 3 or 7 (GND_int) to an external low impedance potential (such as 0V or sensor common terminal) to center the CMP potential of all channels.

For EL3014/EL3024: The internal GND_int has been connected to the 0V power contact, and it should be ensured that the sensor reference potential of all channels is close to 0V. It is strictly prohibited to mix high side measurement (sensor positive pole connected to 24V, negative pole connected to input) with low side measurement (sensor negative pole connected to GND).

5.4 Measurement value jumping or high noise

Possible reasons: electromagnetic interference; The filter is not turned on; Poor grounding.

Solution: Use shielded twisted pair cables, with the shielding layer single ended to terminal point 4 or 8 (Shield). Turn on the 50/60Hz FIR filter. Ensure that the sensor power supply is grounded with the terminal power supply. If the interference comes from devices such as frequency converters, it is recommended to use an independent power supply to power the terminals.