Connecting 4-20mA Sensor to Siemens 6ES7134-6HD01-0BA1 ET 200SP

Overview

The SIMATIC ET 200SP analog input module 6ES7134-6HD01-0BA1 (designation AI 4xU/I 2-wire ST) provides four universal channels that each accept either a voltage (0–10 V) or current (0–20 mA or 4–20 mA) signal. The "2-wire ST" suffix identifies the Standard variant of the ET 200SP AI family: it integrates a short-circuit-proof 24 V sensor supply on every channel and is the variant referenced in the official TIA Portal manual collection for 6ES7134-6HD01-0BA1 and the ET 200SP AI 4xU/I 2-wire ST manual (PDF).

This article explains how to wire a 4–20 mA sensor to channel 2 (terminals I2+ and Uv2) of the module, how to configure the channel in TIA Portal, and how to resolve the field symptoms most often reported: zero reading, stuck-near-zero value, and unwanted influence of channel 2 on channel 0 (cross-talk / common-mode disturbance).

Module Identification and Variant Family

Before wiring, confirm the exact article number on the module label. The same physical module exists in several firmware and feature variants; mixing them up is the most common reason a 4–20 mA sensor "does not work".

The ST suffix indicates Standard (no HART, no high-speed oversampling). If your module reads only current and never voltage, double-check that you have the correct variant before continuing.

Terminal Layout and Pinout

Each channel of the 6ES7134-6HD01-0BA1 occupies four push-in terminals on its BaseUnit. Channel pairs share one BaseUnit (channels 0+1 on the left BaseUnit, channels 2+3 on the right BaseUnit).

For channel 2 the relevant terminals are Uv2, I2+, M2. Uv2 is the integrated 24 V supply that can power a 2-wire transmitter directly. I2+ is the current/voltage input. M2 is the channel ground, internally connected to the backplane busbar.

Prerequisites

1. Hardware: ET 200SP interface module (IM 155-6 PN ST or HF), one AI 4xU/I 2-wire ST module (6ES7134-6HD01-0BA1) with the correct BaseUnit (light BU type A0, or dark BU type A1 if sensor-supply feed-through between channels is required).
2. Power: 24 V DC system supply on the leftmost BaseUnit (typically 6ES7193-6BP00-0BA0 with infeed, or a separate 24 V power module).
3. Software: TIA Portal V16 or later (V17 recommended), with the HSP for ET 200SP AI 4xU/I 2-wire ST installed so that the module appears in the hardware catalog under ET 200SP > AI > AI 4xU/I 2-wire ST.
4. Sensor datasheet: confirm whether the 4–20 mA output is active (sensor sources its own loop power) or passive (loop must be powered externally). Wiring differs between the two.
5. Verification tool: multimeter capable of measuring 0–30 V DC and 0–25 mA DC.

Wiring a 2-Wire Passive Sensor (Loop Powered from Uv)

This is the simplest wiring case and is the connection recommended in the official manual. The module's integrated Uv2 supply powers the sensor and reads the resulting 4–20 mA loop current.

Connection list:

1. Sensor L+ → module terminal Uv2.
2. Sensor L- → module terminal I2+ (this is the same node the current flows into).
3. Channel configured as Current, range 4–20 mA.

Wiring a 3-Wire Sensor (External 24 V Supply)

Most modern pressure, level, and flow transmitters ship as 3-wire devices with dedicated power terminals. Power them from a separate 24 V DC supply (either the system supply or an external PSU) and feed the analog return into I2+.

Connection list:

1. Sensor L+ → external +24 V DC (use the system supply or a dedicated PSU; the module's Uv2 is not used).
2. Sensor L- → external 0 V / M (common ground with the module).
3. Sensor AOut → module terminal I2+.
4. Optionally bond module M2 to the same 0 V node for better noise immunity.
5. Channel configured as Current, range 4–20 mA.

The original poster wired L- to "-24 V power supply" and observed that moving this wire influenced channel 0. That is a classic common-mode symptom: tying the sensor return to a separate ground reference created a ground loop through the analog input. Tie all analog returns to a single star point (typically the module's M terminal or the PSU M) and the cross-talk disappears.

Wiring a 4-Wire (Active) Sensor

Active 4-wire transmitters have an isolated power input and a separate, internally powered current output. Wire them like a 3-wire device but with two dedicated power conductors instead of one supply and one ground. The module variant 6ES7134-6JD00-0CA1 (AI 4xU/I 4-wire ST) is mechanically compatible and recommended when most channels host 4-wire active transmitters, because its Uv rail is disabled to remove one source of ground loops.

TIA Portal Channel Configuration

Hardware wiring alone is not sufficient. Each channel of the 6ES7134-6HD01-0BA1 must be told whether it is a voltage or current input. The default is voltage, which is why a newly-installed channel shows "0" regardless of what is connected to I2+.

1. In the project tree, open Devices & Networks and select the ET 200SP station.
2. Click the AI module to open its Device view.
3. Select channel 2 and open Properties > General > Channel parameters.
4. Set Measurement type = Current.
5. Set Measurement range = 4 to 20 mA.
6. Set Diagnostic > Wire break = enabled (the module drives the current to a defined value when the loop is open).
7. Set Diagnostic > Short circuit to ground = enabled for 2-wire loops powered from Uv2.
8. Set Diagnostic > Overflow / Underflow = enabled to catch range overruns.
9. Set Smoothing = None or Weak; heavier filters increase cycle time.
10. Compile and download the configuration to the IM 155-6 PN.

If your program uses the symbolic I/O names, the analog value appears at %IW<slot> mapped to the configured channel. Channel 2 of the first AI module is typically %IW2 (depends on slot and channel order in TIA Portal).

Parameter Data Record Reference

For advanced users writing their own configuration blocks via WRREC / RDREC, the parameter data record layout for the AI 4xU/I 2-wire ST is documented in the device manual referenced above. The relevant record is data record 128 (channel parameters). Bytes 0–3 control measurement type, range, smoothing, and diagnostics for channel 0; bytes 4–7 cover channel 1, and so on.

Writing the entire 16-byte record with channel 2 set to 0x14 (current, 4–20 mA) and diagnostics enabled is the canonical parameter set for the wiring shown above. The same effect can be achieved more safely through the TIA Portal GUI for everyday use.

BaseUnit Selection

The BaseUnit determines whether and how Uv is supplied. For the 6ES7134-6HD01-0BA1 the common BaseUnit families are:

• BU type A0 (light base, e.g. 6ES7193-6BP00-0BA0) – no internal sensor-supply bridge. Uv is fed only if a power module sits on the left.
• BU type A1 (dark base, e.g. 6ES7193-6BP00-0BA1) – internal sensor-supply bridge, suitable for 2-wire transducers.

Troubleshooting Matrix

Noise and Cross-Talk Diagnosis

The cross-talk symptom described in the field report — channel 0 dropping from a stable 0–27944 to 0–1154 when the sensor return on channel 2 is bonded to "-24 V" — is almost always a common-mode voltage issue rather than a hardware fault. The internal ADC of the AI module measures channel 0 relative to the module's local ground (M). When the channel-2 sensor return is connected to a remote 0 V reference, the difference between the two grounds appears as a common-mode offset that the ADC partially rejects, leaving a residual error proportional to the loop current on channel 2.

1. Disconnect the sensor return from the external "-24 V" node.
2. Connect sensor L- (or L- and the module's M2) directly to the ET 200SP backplane ground. On BU type A0/A1 this is the lower DIN-rail contact strip or the M terminals of the BaseUnit.
3. Measure the voltage between sensor ground and module ground with a multimeter. It should be < 50 mV; anything above that indicates a ground potential difference that needs to be resolved at the panel layout level, not in software.
4. Re-evaluate channel 0 after the change. The reading should stabilise.

Other noise sources to check if the issue persists:

• Sensor cable routed parallel to VFD output cables — re-route with ≥ 200 mm separation or use shielded cable with the shield bonded at one end.
• Missing or damaged shield termination on the analog cable.
• 24 V supply shared with solenoid valves or contactor coils — add an isolated DC-DC converter for the analog loop.

Verification and Commissioning

1. With the sensor disconnected and channel 2 configured for current, the raw value should sit near 0 and the module should report a wire-break diagnostic.
2. Apply a known current (e.g. a 4.00 mA calibrator or a 250 Ω resistor with 1.000 V from a precision source). The raw integer must read 4.00 mA → 0 in engineering units (4 mA = 0 %), 20.00 mA → 27648 (100 %).
3. Verify linearity at 8, 12, 16, and 20 mA. Deviation should be within the module's stated accuracy (typical ±0.3 % of full scale at 25 °C for the 6ES7134-6HD01-0BA1; refer to the device manual for the exact figure that applies to your firmware revision).
4. Toggle the sensor between two known physical setpoints (e.g. empty/full tank) and confirm the engineering range in the PLC program.
5. Force a wire-break by disconnecting one wire; confirm the diagnostic fires and the program takes the configured fallback action.

FAQ