Choosing a Pressure Transmitter Output: 4-20 mA, 0-10 V, I2C/SPI and Wireless
Choose output by host input, distance, supply and data requirements. I²C/SPI typically serves embedded integration, voltage suits compatible acquisition inputs, 4–20 mA suits industrial transmission, RS485 supports compatible networks, and wireless serves distributed points with adequate coverage and power. Availability remains model-specific.
Settle distance and supply first
| Output | Supply SV | Current draw | Load requirement RL (PM160-E example) |
|---|---|---|---|
| 0.5-4.5 V ratiometric | 5.0 +/- 5% VDC | 2.9 mA | 2 kOhm or higher |
| 0.5-2.5 V absolute | 3.2–5 VDC | 2.9 mA | ≥2 kΩ |
| 0-5 V / 1-5 V absolute | 9–30 VDC | 5.9 mA | ≥2 kΩ |
| 0-10 V / 1-10 V absolute | 21–30 VDC | 5.9 mA | ≥2 kΩ |
| 4-20 mA current | 9–32 VDC | — | RL ≤ (SV−8 V)/0.022 A |
This table applies only to the listed PM160-E output versions. The 0.5–4.5 V ratiometric version uses 5.0±5% VDC; this is not a universal supply for every ratiometric sensor. For the 4–20 mA version, RL≤(SV−8)/0.022 gives about 727 Ω at 24 V. Include the receiver, cable and isolator in the total loop load.
4-20 mA: the industrial default
4–20 mA suits industrial transmission, but cable voltage drop still matters: supply must cover transmitter compliance and the total receiver, cable and isolator load. Live zero supports diagnostics with suitable receiver thresholds; fault identification depends on configuration. Confirm two-, three- or four-wire operation for the actual model.
Use the wiring drawing for the actual ordered model, output variant and connector. An M12 or Hirschmann pin-out is not universal across products. Confirm shielding, grounding, colours and host input type; do not wire by colour or connector appearance alone.
Voltage output: ratiometric is not the same as absolute
| Type | Zero level | Supply | Characteristic |
|---|---|---|---|
| Ratiometric | 0.5 V | 5.0 +/- 5% VDC | Output tracks supply; using the same ADC reference can reduce the effect of shared supply variation |
| Absolute | 0.5 V, 0 V or 1 V, by output | 0.5–2.5 V: 3.2–5 V; 0–5/1–5 V: 9–30 V; 0–10/1–10 V: 21–30 V | Lower supply dependence; check model limits |
Also check supply dependence and output limiting for the selected version. The PM160-E absolute-voltage specification lists supply dependence below 0.1% FS per 10 V. Normal output clamping and the fault-output level are different values; use the relevant transfer-curve table rather than applying one clamp voltage or current to every output.
I2C / SPI: choose it for temperature and low power
The value of a digital output is not merely noise immunity — it is that one device reports both pressure and temperature, and can enter a low-power mode. The RS PM160-DV dual-output sensor offers I2C and SPI, runs from 3.0-5.5 V, draws 115 uA in sleep, and its temperature channel measures media temperature.
For PM160-DV, check logic levels, bus capacitance, pull-ups and wiring. The datasheet recommends 10 kΩ I²C pull-ups; the actual resistance must meet rise-time requirements for the chosen speed and capacitance. The sensor has no internal level translation. M12 supports voltage or I²C; confirm SPI and dual mode on the cable version.
Modbus 485 and wireless: networking and remote duty
| Option | What it solves | Cost | Typical use |
|---|---|---|---|
| Modbus 485 | Multi-drop networking over long distances, direct to a host | Requires a bus cable plus addressing and protocol setup | Several transmitters on one acquisition system |
| NB-IoT / 4G | No cabling at all, battery operation possible | Connectivity charges; coverage and power budget matter | Pipe networks, remote sites, scattered points |
RS WA30 is available with 4–20 mA, voltage or RS485 output; confirm the ordered version and its protocol. PM350-RTU supports NB-IoT / 4G and RS485 Modbus pressure output. Wireless reports pressure and temperature, while the listed RS485 channel provides pressure. Check each interface and configuration separately.
A decision table
| Your situation | Recommended output |
|---|---|
| Longer or noisy runs, with loop-load calculation | 4-20 mA |
| Short in-cabinet run, voltage input module already present | 0.5–4.5 V / 0–10 V / 1–10 V |
| 5 V microcontroller system, battery powered | 0.5-4.5 V ratiometric |
| Temperature also needed, or low power required | I2C / SPI |
| Several transmitters networked, digital values wanted | Modbus 485 |
| No cabling or mains power available | NB-IoT / 4G wireless |
Four checks before ordering
- Supply voltage falls inside the range for that output (a 5 V ratiometric unit on 24 V will be destroyed).
- Load meets the selected output requirement; for the PM160-E 4–20 mA version use RL≤(SV−8)/0.022.
- Connector pinning checked against the output type — current and voltage versions differ.
- Zero and full-scale levels agreed (for example 0.5-4.5 V versus 1-5 V) and written into the purchase specification.
Next step
Available output combinations and full electrical data for each series are in the datasheets on the downloads page. Where pressure and temperature are both required from one device, start with the RS PM160-DV or the calibrated RS PMSC350 core (0.5-4.5 V and I2C).
More answers in the FAQ.
Related documentation: RS WA30 · RS PM350-RTU
Specifications: View PM160-E datasheet (PDF) · Download PDF · View PM160-DV datasheet (PDF) · Download PDF