Application
Measuring input and output power, efficiency and electrical parameters on motors, drives and pumps.
Motor and drive testing compares electrical input against mechanical or thermal output, so efficiency is the headline result and every measurement error propagates into it. Both sides of the ratio have to be trustworthy at once, because a small error on either side shifts the answer directly rather than being averaged away.
A variable-frequency drive adds a complication that does not exist on a fixed supply. Its output is neither sinusoidal nor at a constant frequency: it is a switched waveform whose fundamental changes with speed. The practical requirement that follows is measurement bandwidth. An instrument that integrates over a period longer than the drive switching cycle produces a stable but incorrect figure, and the error grows as the output becomes more distorted, which tends to be at the low-speed end where the drive is most often run.
Thermal testing compounds both problems because it runs for hours. Winding and bearing temperatures, coolant flow and electrical readings all have to be captured over the same period and aligned in time, so the ability to log and export is a specification point rather than a convenience.
| Measurement | What the reading has to establish | Instruments commonly specified |
|---|---|---|
| Input and output electrical power and efficiency | Whether the machine meets its declared efficiency across the speed range rather than only at the rated point | Digital power meters with AC/DC and multi-phase capability |
| Current without breaking the circuit | Loading on a machine that is already installed and cannot be taken out of service for a tap | Clamp meters |
| Winding and bearing temperature | Whether the thermal limit is reached during a sustained run, and how quickly | Temperature measurement and transmitters |
| Coolant and lubrication flow | That the cooling duty assumed in the efficiency calculation is actually being delivered | Flow measurement |
| Torque and speed at the shaft | The mechanical output side of the efficiency ratio, which cannot be inferred from current alone | Industrial sensors and load cells |
Where the machine is fed from a drive, the power figures on both sides of the drive matter, not only those at the motor terminals.
| Adjacent application | What separates it from motor and drive testing |
|---|---|
| Electrical parameter testing | That work is taken on a steady supply at one operating point, so bandwidth never becomes a deciding factor. |
| Power supply testing | There the waveform is fixed and the difficulty is at the bottom of the range, while here the range is wide but the waveform itself is the problem. |
| Energy efficiency testing | That work accumulates consumption over a standard cycle, whereas here the machine is exercised across its own speed range and the result is a curve rather than a single figure. |
| Industrial test bench & calibration | A bench checks whether a measuring instrument is honest; a drive test checks whether a machine performs, using instruments assumed to be honest. |
| Product quality inspection | Inspection is a pass-fail decision on a finished article, while this work produces performance data used to design or to declare. |
Published products
3266TA (3 models) · Clamp Meters
Clamp meter range reading current through a 25 mm jaw without breaking the circuit, from an AC-only model up to an AC/DC instrument with true-RMS conversion, 6000 counts and a 100 mF capacitance range.
AMX-HM · PLC Systems
Programmable logic controllers with an integrated touch screen, in 4.3, 7 and 10 inch formats, combining discrete and analogue I/O, PT100 inputs, high-speed counting and relay outputs in one panel unit.
CXT2518-4 (5 models) · Electrical Test Equipment
Bench scanners that step a four-wire measuring circuit through 2 to 64 channels, applying per-channel limits, in ranges from 1 µΩ to 2 MΩ and at up to 40 readings per second.
CXT3513 · Electrical Test Equipment
Benchtop tester measuring the three winding resistances of a three-phase motor from 10 µΩ to 20 kΩ, calculating spread and unbalance for star or delta connection and sorting against limits.
HG3030 · LCR Meters
Three-channel DC resistance tester for motor windings, covering 10 µΩ to 2 MΩ at 0.05% accuracy, with simultaneous three-phase display, percentage comparison and pass or fail sorting.
HG7683 (2 models) · Insulation Resistance Testers
Bench insulation resistance meter with a voltage range from 1 V, resistance to 100 TΩ, three measuring speeds, five-bin sorting and 600 stored records on the wide-range model.
HG9813 (4 models) · LCR Meters
Four impulse winding testers reaching up to 10 kV, with corona analysis, high-speed waveform capture, a 7-inch colour display and pass or fail outputs for inter-turn insulation testing of coils and windings.
SJ2511 (6 models) · Electrical Test Equipment
Bench four-wire DC resistance meters covering 0.01 µΩ to 2.4 GΩ across the group, with basic accuracy from 0.006% to 0.1%, test current to 10 A and three-level comparator sorting.
SJ2682A (6 models) · Insulation Resistance Testers
Benchtop insulation resistance meter with programmable direct voltage from 0.5 V, resistance ranges to 100 PΩ on the top model, micro-current measurement from 0.1 fA and four-bin sorting.
TH2882A-3 (3 models) · LCR Meters
Impulse winding testers that apply a high-voltage pulse to a coil and compare the response waveform against a reference, for finding inter-turn shorts, weak insulation and winding faults in single-phase and three-phase parts.
UTD2102CEX+ (3 models) · Electrical Test Equipment
Two-channel digital storage oscilloscope with 100 MHz bandwidth, 1 GSa/s sampling, 64 kpoint memory, a 7 inch display and recording of up to 1000 screens.
Frequently asked
The questions that come up before an order. If yours is not here, send it with the duty and we will answer it alongside the quotation.
A drive output is a switched waveform. If the instrument integrates over a period longer than the switching cycle it cannot capture the true RMS value of the current, so efficiency figures are systematically wrong, and the error grows as the drive output becomes more distorted.
Where the instrument has enough channels and the right isolation, yes. Otherwise two units are used, and the readings then have to be taken over the same period if an efficiency figure is to be calculated from them.
If the result has to be mechanical efficiency, the shaft output is needed, and current alone cannot substitute for it because the relationship between current and torque changes with the drive settings. If only electrical losses are of interest, the measurement stays on the electrical side.
At low speed the fundamental frequency is low and more of the waveform is switching content. An instrument with limited bandwidth sees a larger proportion of distortion as error, so the figures obtained at low speed are usually the least reliable of the run.
Only where it has the bandwidth and the crest factor tolerance to handle a switched waveform. A general-purpose clamp meter intended for mains work will typically under-report on drive output, which flatters the efficiency figure.
The machine rating, the drive model or its switching frequency, the phase arrangement, and which quantities have to appear in the result. Those four answers usually fix the instrument family before any catalogue is consulted.
Send the measurand, the range and the conditions, and we will confirm the instrument family, the configuration and the lead time.
Request for quotation
Send the technical detail and we will confirm availability, lead time and terms. In-stock items ship within 48 hours; customized specifications typically take 2-10 days. Minimum order quantity is 1 pc.