Why does my Tecweigh say zero belt speed when the belt is running?

We’re an independent service company, not a Tecweigh dealer or agent. For bookings and parts, see Tecweigh belt weigher and WP-series servicing. For the other WP50 messages, see what the messages on a Tecweigh WP50 mean, and for the same fault on any brand, see no speed, or the total has stopped climbing.

What does zero belt speed mean on a Tecweigh?

The scale card at the weigh frame reads the speed sensor and load cells, then sends speed, load and scale status to the processor over a serial link. When the pulses stop, the card reports zero belt speed. On a WP50 that’s no pulses for more than half a second; the older manuals don’t give a time. Rate is belt loading multiplied by belt speed, so zero speed means zero rate. A speed that’s wrong rather than missing costs more and says nothing.

Is it a fault, or is the belt just stopped?

Often it’s just stopped. On every generation the first listed cause is a belt that isn’t moving, and the commissioning procedure uses the message to prove the scale works: stop the belt, see it appear, restart, see it clear.

The test needs no tools. From a safe position, watch the displayed speed while the belt is visibly running. Zero on a moving belt is a signal fault. Don’t confuse it with a low belt speed alarm, which is a relay someone set up with their own limits, or rate in deadband, which stops the total with no speed fault at all.

Which box does the speed sensor wire into?

On a WP20 and a WP50, the scale card at the weigh frame. Only power and a serial pair run back to the processor, which can be up to about 1,200 m away, and the cause list names the cable between the sensor and the scale card, never one to the processor.

The WP25 can be wired either way: direct into the processor enclosure, or through a scale card at the frame. Work out which you have first. Several scale card families are in service with different options, so a photo of the card beats a model number read off the panel. For the older processors, see Tecweigh WP20 and WP25 fault codes and calibration.

Why does the speed light look solid when the sensor is fine?

Work on or near a conveyor, or inside an electrical enclosure, needs isolation under your site’s procedures and trained, authorised people. If that’s not you, stop and call us on 1300 101 666.

With the belt running, the green speed indicator on the scale card should blink, and every edition of the manual warns that a fast blink can look solid. Misread it and a healthy sensor gets replaced while the fault stays put.

If it really isn’t blinking, the documented causes are the sensor or its circuit, a failed scale card, or no supply at the card. The supply indicators split those: green means adequate supply, red means insufficient supply or a failed board. We don’t quote a voltage, because the thresholds differ between card generations.

What’s the fastest way to take the speed sensor out of the picture?

Switch on the scale card’s simulated speed. If a speed appears, the card and everything inwards works, and the fault is out at the sensor, cable or wheel. The simulated figure comes from the scale’s own speed span setting, so you know what to expect. Add the calibration weight and both load and speed are fixed: a rate that’s still unsteady is vibration or noise, not weighing. See why belt weigher totals are erratic.

We don’t name switch positions, because they differ between card families and manual editions. Switch the simulated speed off before leaving site, or the scale will count on a stopped belt.

Why does a new speed sensor sometimes make it worse?

The scale card has to be set for the sensor style. A sensor that produces a voltage needs part of it loaded down at the card. Magnetic pickup, open collector and logic level sensors need that loading off, and open collector also needs a pull up at the card. Swap styles without changing the card and you can get no speed, a wrong speed or a damaged input. The WP25 manual names a wrong sensor switch setting as a cause of this message.

Whatever is fitted, check the speed against a timed run afterwards. More than about 2% off a measured speed needs investigating. If you’re choosing a replacement, our USR speed sensor mounts on the tail drum or as a trailing arm, and its multiple outputs let one sensor feed two belt weighers, or a belt weigher plus the conveyor underspeed. We’ll confirm it suits the scale card input first. See which speed sensor a belt weigher uses.

Could a noise setting be hiding a slow belt?

Yes. The card’s noise and vibration options raise the bar a real signal has to clear. With the vibration option on, speeds below roughly 6 m/min may not be detected with the standard sensor (converted from feet per minute). A speed multiplier option is suggested for belts slower than about 5 m/min, and the speed must be calibrated again after using it. So if the message only shows at low drive speeds, check the card settings before the sensor. If noise is the real problem, see protecting belt weigher electronics.

What should the speed sensor wheel be doing?

Riding on the return side of the belt, aligned with it, roughly 150 to 300 mm clear of a return idler (converted from inches), and free to swing. A wheel that isn’t straight bounces and wears, so a chewed wheel is a mounting problem. A wheel that won’t turn freely means a sensor replacement. Grease the speed sensor bearings monthly. The other named causes are the dull ones that are often right: loose terminals, and a broken or shorted cable to the scale card.

Can you keep totalising while a speed sensor is on order?

Yes. A WP50 can use a typed in belt speed with manual speed enabled, and a WP25 has an artificial belt speed in its maintenance menu. The load is still weighed, but the speed is a number someone chose, so record those tonnes as an estimate.

Nothing on the WP50 alert list announces it, and neither unit documents it clearing itself, so it comes off deliberately or not at all. Unlike WP25 simulation, which puts the real total back afterwards, a typed in speed feeds the real totaliser. We log what was enabled and when it has to come off in AIMM, our asset management system.

What if the speed shows with the belt stopped?

That invents tonnes instead of losing them. Usually it’s a simulated speed left on at the scale card, a typed in speed still enabled after a sensor swap, or electrical noise counted as pulses. We check for these on arrival at any scale we didn’t commission. See also why a belt weigher reads a flow rate on an empty belt.

We supply parts for Tecweigh and the other major belt weigher brands: a genuine part where it’s available, or a suitable alternative, with compatibility confirmed and the part identified on the quote.

Need a manual for your equipment?

For this fault you usually need the processor manual and the document for the scale card at the frame, which covers the sensor style settings and the slow belt and noise options. Photograph the card itself, because card families differ and switch positions don’t carry across.

Talk to us about manuals for your equipment. Send the make, model, serial number and software version (a photo of the label is fine) and we’ll help you find the right document.

When should you call us?

Call when the wheel is turning and the reading isn’t, a new sensor changed nothing, the fault comes and goes or follows the weather or drive speed, or nobody has a record of the unit’s settings. On site we read the raw speed count the WP50 shows from the scale card, check the card settings against the sensor actually fitted, and time the belt before anything is calibrated. Don’t calibrate over a speed fault: it writes the error in and throws away the evidence. Call 1300 101 666 or email admin@accurateindustries.com.au. See booking a belt weigher service.

Frequently asked questions