Accelerometer Cable Guide: 2-Pin vs 3-Pin, Armoured & IS Options

A pump bearing accelerometer that reads clean on the bench can go noisy the moment it's wired through a cable tray back to the data collector twenty metres away — not because the sensor's faulty, but because nobody thought about shield grounding or cable length until the readings started drifting.

2-Pin vs 3-Pin: Which Accelerometer Cable Do You Actually Need?

Most top-connector piezoelectric accelerometers used in condition monitoring run on a 2-pin cable — one conductor for signal, one for return/shield. That covers the majority of vibration monitoring points on pumps, motors and fans. A 3-pin cable comes into play when the accelerometer or the data collector interface calls for a separate case ground or a third reference conductor — in practice, this is more common on certain triaxial mounting setups or where the collector manufacturer specifies it. Before ordering, check the connector spec on the accelerometer itself rather than assuming pin count from the sensor's physical size.

The same logic carries over to eddy current probe cables, which run alongside accelerometer cable on most reliability jobs. These are typically supplied as a matched pair (probe cable to extension cable) with a fixed pin configuration set by the probe manufacturer — swapping in a generic cable here usually isn't an option.

Armoured or Non-Armoured: Matching Cable to the Route

If the run from bearing to data collector stays inside a cable tray or conduit for its full length, non-armoured ETFE-jacketed cable is usually sufficient and easier to terminate on site. Once the route crosses open floor space, drags near rotating equipment, or sits somewhere it could be stepped on or caught by a forklift, armoured cable earns its keep — the steel braid under the jacket protects the signal conductors from the kind of mechanical damage that shows up as intermittent readings months later rather than an immediate failure.

This is where sizing your instrumentation cable run properly matters just as much for accelerometer cable as it does for multi-pair signal wiring — a cable that's technically long enough but poorly protected along the route will cost more in re-runs than choosing armoured from the start.

Intrinsically Safe vs Shield-Grounded: Getting the Earthing Right

Standard shield-grounded accelerometer cable is fine for most process plants — the shield ties to ground at one end (typically the data collector side) to avoid ground loops, which is the usual cause of 50Hz hum riding on the vibration signal. If the monitoring point sits in a classified hazardous area — a gas compressor skid or a fuel storage area, for example — intrinsically safe (IS) rated cable becomes a compliance requirement, not a preference. IS-rated cable is built to limit the energy that can reach the hazardous zone, and it typically needs to be installed and terminated according to the site's IS loop drawings rather than general good practice.

Getting Cable Length Right, From Sensor to Data Collector

It's tempting to grab whatever length is on the shelf and coil the excess, but excess coiled cable can act like an unintended antenna and add noise to a low-level signal. As a general rule, it's better to measure the actual run — sensor mounting point to junction box or portable collector position — and order the closest length above that, rather than rounding up generously. For permanent installations feeding a data collector via a Lemo-style connector, this matters even more, since the connector end is usually fixed and can't be trimmed and re-terminated on site the way a standard shielded cable can.

The same length-matching principle applies to fibre optic temperature probe extension cable, which often runs the same route as accelerometer cable on bearings that are monitored for both vibration and temperature. If that's part of your scope, it's worth reading how to choose between multimode and singlemode fibre for the temperature probe side of the run, since the wrong fibre grade over a longer run can cause its own signal loss issues — separate from anything on the accelerometer side.

Common Mistakes with Accelerometer Cable Selection

Ordering by physical fit instead of pin assignment. A 2-pin and 3-pin connector can sometimes look similar enough at a glance that the wrong cable gets pulled from stock — always cross-check against the sensor data sheet, not the connector shape.

Grounding the shield at both ends. This is one of the most common causes of noisy vibration data — grounding both ends creates a ground loop. The shield should typically only be earthed at one end of the run.

Using non-armoured cable across an exposed route to save cost. It works fine until the first forklift pass or foot traffic incident, after which the fault can be intermittent and genuinely difficult to trace back to physical damage.

Coiling excess cable instead of measuring the run. Coiled cable behaves differently to a straight run electrically, and it's an easy way to introduce noise that wasn't there on the test bench.

Assuming standard cable is fine in a hazardous area. IS-rated cable and standard shield-grounded cable are not interchangeable in a classified zone, regardless of how similar they look on the reel.

Frequently Asked Questions

Cable Selection

do I need 2-pin or 3-pin accelerometer cable?

Check the connector spec on the accelerometer's data sheet. Most top-connector piezoelectric accelerometers use 2-pin; 3-pin is used where the sensor or collector interface calls for a separate reference conductor.

can I use the same cable for accelerometer and eddy current probe?

Not usually. Eddy current probes are typically supplied with a matched probe-and-extension cable set from the manufacturer, while accelerometer cable is generally sourced separately — see the instrumentation and multi-pair screened cable range for both.

Compliance & Hazardous Areas

do I need IS-rated cable for a bearing sensor near a gas compressor?

If the point sits inside a classified hazardous area, IS-rated accelerometer cable is typically required under AS/NZS 60079 in Australia. Confirm the zone classification with the site's electrical engineer before installing.

is a licence required to terminate accelerometer cable on site?

Terminating low-voltage instrumentation cable in Australia generally falls under the same licensing requirements as other electrical work, though scope can vary by state and site. Check with the relevant state licensing authority and the site's electrical safety rules before starting work.

Length & Installation

why is my accelerometer reading noisy after a long cable run?

Common causes include shield grounded at both ends (creating a ground loop), excess cable coiled rather than run straight, or non-armoured cable picking up interference near motors and VFDs along the route.

what length accelerometer cable do I need for a 15m run?

Measure the actual route from sensor mount to junction box or collector, then order the closest standard length above that figure — for a genuine 15m run, a 15m armoured 2-pin shielded cable avoids both a short-fall and excess coiling.

can accelerometer data collector cable be extended?

Cables terminated with a Lemo-style connector to the data collector are generally supplied as fixed-length assemblies and aren't designed to be field-extended or re-terminated — order the length matched to your actual collector-to-sensor distance up front.

Shop Accelerometer Cable at Schnap

Trade pricing and same-day dispatch from Kingsgrove NSW across the accelerometer, probe and data collector cable range.

• 2-Pin Accelerometer Cable
• 2-Pin 5m Shield-Grounded -- standard shield-grounded cable for short runs
• 2-Pin 10m Shielded -- ETFE-jacketed, non-armoured
• 2-Pin 15m Armoured -- for exposed cable tray or high-traffic routes
• 2-Pin 20m Intrinsically Safe -- for classified hazardous area installs

• 3-Pin Accelerometer Cable
• 3-Pin 5m Shielded -- for sensors requiring a third reference conductor
• 3-Pin 19m Shielded -- longer runs with third-conductor sensors

• Data Collector & Probe Cable
• 2-Pin Lemo 2m Coiled -- short flexible lead to portable collectors
• 2-Pin Lemo 15m -- fixed-length assembly for longer collector runs
• Probe Cable 152m Non-Armoured -- bulk cable for multi-point installs

• Eddy Current Probe Cable
• 4m Non-Armoured -- matched extension for short probe runs
• 4m Armoured -- protected extension for exposed routing
• 8m Armoured -- longer armoured extension
• 4.5m Armoured -- compact armoured probe extension

Browse the full accelerometer cable range at Schnap for trade pricing and same-day dispatch from Kingsgrove NSW.