Electrical Test & Measurement · Power Meters
Panel digital power meter reading voltage, current, active power, power factor, frequency, apparent and reactive power in four windows at once, with an RS232 Modbus RTU port as standard and current ratings from 20 A to 200 A.
YP9901 (3 models) ·
A power meter is bought to answer what a load is doing rather than what a supply is capable of. The instrument reads voltage and current at the same instant and computes everything else from that pair, which is the reason it cannot be replaced by two separate readings taken one after the other.
The range covers single-phase measurement across three series. The alternating-current series is built for general electrical verification, a second version is aimed at efficiency work where the interesting figure sits far below rated load, and the third adds direct-current measurement for adapters, chargers and DC supplies.
What separates them in use is not resolution but the two ends of the current span. The top of the range decides the largest unit that can be tested, and the bottom decides whether a standby figure is a measurement or only a number on a display. Both ends are quoted per rating rather than per instrument, which is why a quotation for this family comes back as a series and a rating rather than as a model number alone.
Voltage across the load and current through it are sampled together and converted against a single timebase. Multiplying the two point by point and averaging the result over a whole number of cycles gives active power directly, without assuming that the waveform is sinusoidal or that the load is linear. Power factor then follows as the ratio of active power to the product of the root-mean-square voltage and current, and apparent and reactive power come from the same three quantities.
That arithmetic is the reason the instrument exists in this form. A rectified average multiplied by a rectified average gives the right answer only on a clean sine wave; a switched-mode supply, a dimmer or a drive produces a waveform for which the two differ, and the error runs in one direction. An instrument that samples and multiplies does not care about the shape of the waveform, which is why the same instrument can be trusted on both a heater and a power supply.
Three answers settle the selection. The first is whether the duty includes direct current: if an adapter, a charger or a DC supply is to be characterised, the alternating-current series cannot substitute and the decision is made. The second is the current span at both ends, taken from the largest unit to be tested and the smallest consumption figure the test standard names. The third is the nature of the load, because a drive or a switching supply requires a conversion that agrees with the readings taken around it.
The remaining choices are made once and then fixed. A low-current series is the difference between measuring standby consumption and merely displaying it. An energy total with elapsed time turns a run into a consumption figure. An isolated bus or a relay output has to be ordered with the instrument, since neither can be added afterwards.
This instrument characterises a load at a bench or a test position. It does not diagnose the waveform that produced the reading: harmonic content, distortion, unbalance and transients belong to a power quality analyser, which is a different instrument with a different purpose. Where the question is why a figure is what it is rather than what the figure is, the power meter is the wrong end of the diagnostic chain.
Two operational limits follow from the same construction. High currents pass through an external shunt, so the accuracy of the highest ratings depends on a component that may not be part of the instrument; and the basic class figure applies under calibrated conditions, with the error growing as the power factor falls. Both are reasons to state the duty in the enquiry rather than to select from the parameter table alone.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| Basic accuracy | ±0.2 %, stated by the material as 0.2 classStandard |
|---|---|
| Reference standard behind the class | Not stated in the materialInformation required |
| Power factor range | 0.000 to 1.000 on the alternating-current series and the AC/DC series; 0.001 to 1.000 on the efficiency seriesStandard |
| Frequency range | 40 to 1000 Hz in the function specification, and 40 to 400 Hz in the selection table and the supply line; both carried as printedInformation required |
| Energy accumulation | Elapsed time and accumulated energy, displayed in kWh or in hoursStandard |
| Peak registers | Highest voltage, current, active power, apparent power and reactive power seen during a runStandard |
| Conversion method | The material does not state whether the alternating channels compute a true root mean square value or an average of the rectified waveformInformation required |
| Repeatability | Not stated in the materialInformation required |
| Voltage range switching | AutomaticStandard |
|---|---|
| Voltage input impedance | About 2 MΩ, stated for the voltage channelStandard |
| Current ratings | 20 A, 40 A, 80 A, 100 A and 200 A, according to seriesStandard |
| High-current connection | The 100 A and 200 A ratings of the AC/DC series are used with an external shunt; whether the shunt is supplied is not statedInformation required |
| Update rate | Settable from 1 to 20 readings per second, with fast, 200 ms and slow positionsStandard |
| Overload capacity | Not stated in the materialInformation required |
| Working temperature and humidity | Not stated in the materialInformation required |
| Ingress protection | Not stated in the materialInformation required |
| Serial port | RS232 with Modbus RTU, fitted as standardStandard |
|---|---|
| Optional interface | Isolated RS485 or a relay output, ordered with the instrumentOptional |
| Supply voltage | 220 V nominal, or a wide-range 85 to 265 V AC / 100 to 300 V DC inputStandard |
| Supply frequency | 40 to 400 Hz as printed in the supply line of the materialStandard |
| Channel isolation | Not stated in the materialInformation required |
| Body | 300.2 × 215 × 100.6 mmStandard |
|---|---|
| Panel cut-out | 210 × 95 mmStandard |
| Weight | About 2.3 kgStandard |
| Case | Metal housingStandard |
| Rear connections | Load connector, supply socket and source terminalsStandard |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| YP9901 | Alternating current only, single-phase, LED display, five current ratings from 20 A to 200 A | 3 to 600 V AC; 5 mA to 20 A up to 20 mA to 200 A according to rating; power factor 0.000 to 1.000 | The general series for alternating-current measurement. The 200 A rating starts at 20 mA rather than at 5 mA |
| YP1020 | Alternating current only, for efficiency work, in a five-level and a six-level version | Power factor 0.001 to 1.000; lowest current from 0.5 mA on the 20 A version and 0.05 mA on the 40 A version | The series for standby and no-load consumption, where the figure of interest sits two or three decades below the rated load |
| YP2012 | AC, DC and RMS, five current ratings from 20 A to 200 A | 3 to 600 V AC + DC; 3 mA to 20 A up to 50 mA to 200 A; the 100 A and 200 A ratings use an external shunt | The only series that can characterise a direct output, and therefore the one required for adapters, chargers and DC supplies |
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
Whether any part of the duty is direct current. An adapter, a charger, a DC supply or a battery has an output that an alternating-current channel does not measure, so those duties force the AC/DC series. A mains-fed motor or a heater does not, and the alternating-current series is the simpler and less expensive choice for them.
Because the top of the range decides the largest load that can be tested and the bottom decides whether the smallest figure is a measurement or merely a number on a display. Standby and no-load consumption sit at the bottom, and an instrument whose lowest range is in milliamperes will report them poorly however good its accuracy class is.
It is the basic error of the instrument under calibrated conditions, and the material points out that the figure in service also depends on the range in use, the power factor, the distortion of the waveform and the way the instrument is wired. At a low power factor the error grows well beyond the class figure, which is why the class alone does not describe how well a particular test will go.
The supply and whether direct current is involved; the largest and smallest currents the tests require; the accuracy figure and the standard behind it; whether standby consumption is measured; the nature of the load, since a non-sinusoidal waveform requires a true root mean square conversion; whether a controller reads the result and over which interface; whether energy over a run has to be reported; and how the instrument is mounted.
Related products
DT9205A (3 models) · Digital Multimeters
Handheld digital multimeter with a 1999-count display and 32 ranges covering AC and DC voltage and current, resistance, capacitance, diodes and transistors, with continuity, overload protection and automatic switch-off.
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.
AC-10A (3 models) · Panel Meters
Panel meter showing AC voltage and current together on two rows of digits, self-powered from the measured circuit and supplied with a split-core current transformer.
Send the configuration you need and we will confirm availability, lead time and terms. Minimum order quantity is 1 pc.
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.