4-20 mA vs 0-10 V: Which Analog Signal to Specify (Spec-First Basics)
Spec-First Basics, part 1. Find it by part number. Buy it with the specs in front of you. This guide compares the two most common analog signals in panels and field instruments, 4-20 mA current and 0-10 V voltage, so you can pick the right output option on a transmitter, valve actuator or signal converter before you order.
Quick answer
Specify 4-20 mA for field instruments, long cable runs and anything where you must tell a broken wire from a zero reading. Specify 0-10 V for short runs inside one panel or building, where the receiving input only accepts voltage. If the two sides do not match, put a DIN-rail signal isolator/converter between them.
Specs at a glance
| Spec | 4-20 mA (current loop) | 0-10 V (voltage) |
|---|---|---|
| Zero point | 4 mA (“live zero”) | 0 V |
| Broken-wire detection | Yes: a reading near 0 mA means an open loop | No: a cut wire reads like 0 V (zero) |
| Effect of cable resistance | Current is the same everywhere in the loop, so line resistance does not change the reading (within the supply’s loop budget) | Voltage drop on the cable lowers the reading |
| Typical wiring | 2-wire (loop-powered) or 3/4-wire | 3-wire (supply, signal, common) |
| Typical use | Field transmitters, PLC/RTU analog inputs, long runs | HVAC controls, drives and short in-panel runs |
| Convert to voltage | 250 Ω resistor turns 4-20 mA into 1-5 V | Needs an active converter to become 4-20 mA |
Questions and answers
Why does 4-20 mA start at 4 mA instead of 0?
The 4 mA “live zero” keeps a loop-powered transmitter running at the bottom of its range and lets the receiver separate a real zero (4 mA) from a fault (near 0 mA). Many systems follow NAMUR NE 43, which treats signals below 3.6 mA or above 21 mA as a fault.
How do I scale a 4-20 mA signal to engineering units?
Value = range low + (mA − 4) ÷ 16 × (range high − range low). Example: a 0-10 bar transmitter reading 12 mA gives 0 + (12 − 4) ÷ 16 × 10 = 5 bar. Use the free 4-20 mA scaling calculator to check any range.
How do I scale 0-10 V?
Value = range low + (V ÷ 10) × (range high − range low). A 0-10 V signal of 2.5 V on a 0-100 °C range is 25 °C. Remember that a cut wire also reads 0 V, so the controller cannot tell it from a true zero.
When is 0-10 V the better choice?
When the device that reads the signal only has voltage inputs, and the cable stays short and away from motor leads. Many valve actuators and drives accept both; for example the motorized V-port ball valve below takes 4-20 mA, 0-5 V or 0-10 V as its control input.
My PLC has 4-20 mA inputs but the sensor outputs 0-10 V (or the reverse). What do I buy?
A signal converter that accepts the sensor’s signal and outputs what the PLC expects. A DIN-rail isolator also separates the two grounds, which helps when the field device and the panel are powered from different supplies.
Is RS485 a replacement for both?
RS485 (usually Modbus RTU) carries the reading digitally and can put several devices on one pair, but the receiver needs a serial port and the right register map. Several transmitters in our catalog offer 4-20 mA, 0-10 V or RS485 as separate output options: choose the variant that matches your input card.
Products that list these outputs
| Product | Signal options (from the listing) | Price |
|---|---|---|
| G1/2 industrial pressure transmitter (supplier model QDW90A) | 4-20 mA, 0-10 V or RS485, 24 VDC; ranges from -1…0 bar to 0-600 bar | from $62.99 |
| DIN-rail PT100 temperature transmitter | PT100 in, 4-20 mA out, 24 VDC; ranges from 0-50 °C to 0-500 °C and -50 °C options | from $32.99 |
| 4-20 mA signal isolator and converter, 35 mm DIN rail | In: 4-20 mA, 0-20 mA, 0-5 V, 0-10 V. Out: the same four. 1 to 4 outputs, 24 VDC | from $52.99 |
| Motorized V-port proportional ball valve, SS304 | Control in: 4-20 mA, 0-5 V or 0-10 V. Feedback: 4-20 mA or OC/PWM. DN8 to DN25 | from $165.99 |
Prices are the current prices on each product page; check the page for the variant you need. Free US shipping on every order.
Before you order: checklist
- Input type on the receiver (PLC card, RTU, meter): current or voltage, and its range.
- Supply voltage the transmitter needs (the products above list 24 VDC).
- Measuring range: pick the variant whose range covers your normal operating point with margin.
- Cable length and routing near motor or VFD leads: longer and noisier favors 4-20 mA.
- Whether you need isolation between field and panel grounds.
Not sure which transmitter fits a pressure, level or temperature point? Use the 3-question transmitter selector. Buying for several panels or sites? Request a written volume quote on the quote request form.