Line Power Meter

Measurement of line power,




The Line Power Meter is designed to measure characteristics of 120 Volt AC line power delivered to a typical household or office load. It consists of a remote sensor unit and a tabletop display unit. The sensor and display units may be used sidebyside, or separated across a room or small building for more convenient installation and monitoring.


The remote sensor unit is connected to an outlet using a standard IEC power cord, which is attached to the sensor unit at a fused power entry jack (on the rear panel of the unit shown).
The load, which may be a power bar, is then plugged into the outlet on the sensor unit (on the front panel of the unit shown).
The remote sensor is connected to the display unit using a standard CAT5 LAN cable of convenient length, attached to the remote unit at a standard RJ45 jack (also on the front panel of the unit shown).
The line power and other quantities shown at the display unit are all determined from measurement of instantaneous voltage and current at the remote sensor unit.


The displayed electrical service characteristics include the true RMS AC line voltage and current, average real (W), apparent (VA) and reactive power (VAR), and the power factor. Energy consumption and cost rates are displayed for day, month and year periods (ex. kWh/day, $/day), based on the measured power and a utility charge rate (cents/kWh) set by the user. The meter will also keep track of the total energy consumption and cost (kWh, $) over many days or months.




Main display – showing true RMS AC line voltage and current, average real power, and the cost per day. The voltage and current are computed from their respective instantaneous waveform measurements. The real power delivered to the load is computed as the product of the voltage and current waveforms. The average real power (W) is then the average value (over many cycles) of this instantaneous power. The cost per day is estimated from the average real power, based on the utility charge rate (cents/kWh).


Power Factor – showing average real power, apparent power, power factor and reactive power. The apparent power (VA) is computed as the product of the values of RMS AC voltage and current. The power factor is computed as the ratio of the average real power (W) to the apparent power (VA). The reactive power is computed as the difference between the apparent power (VA) and the average real power (W).




Energy Rate – showing average real power (W), and the energy consumption this represents in kWh per day, month and year. (note 1000 W = 24 kWh/day)


Cost Rate – showing average real power (W), and the cost ($) that this would incur over a period of a day, month and year. The utility charge rate may be set and stored into memory by the user. (in this case the utility rate is 8.7 cents/kWh)




Total Consumption – showing the time period (hours) over which the energy consumption has been monitored (integrated), the total energy that has been consumed (kWh), and the total cost ($ or cents) of this energy, based on the utility charge rate.




Settings – where the user may select to set temporary zero reference measurement levels, reset the total energy consumption monitor (display noted above), or adjust the utility charge rate.


Zero Reference – Temporary zero reference levels may be set or cleared by the press of a pushbutton. When zero reference is engaged, the voltage, current, power and other computed quantities are shown relative (+/) to their values when the reference was set. (A zero reference may in fact be set or cleared in the same way at any time when viewing other displays above.)


Reset Totals – The total energy consumption monitor (integration) process may be reset at any time. This will set the total hours, kWh and cost ($) all to zero.


Adjust Cost Rate – The cost of power (charged by a typical utility) may be adjusted for immediate temporary use, or may be saved into nonvolatile memory to be automatically loaded whenever the display unit is turned on.

Electrical Specifications

General Architectural:
Voltage: 65.0 – 130.0 Vrms AC (crest factor > 2) Current: 0.10 – 15.00 Arms AC (crest factor > 2) Real Power: 0 – 2000 W Apparent Power: 10 – 2000 VA Reactive Power: 10 – 2000 VAR Power Factor: 0.00 – 1.00 * Specification implies display precision.
Specific Performance: Voltage Accuracy: +/1.0% @ 120V Voltage Crest Factor: ~ 2.8 @ 120V Current Accuracy: 1.0% @ 10A Current Crest Factor: ~ 3.8 @ 10A Power Accuracy: +/2.0% @ 1200 W (pf~1.0) 