Laureate™ True AC RMS Voltage & Current Panel Meters

(0.2 V - 660 V & 2 mA - 5 A full-scale ranges)
  • 0.2, 2, 20, 200 & 660 V ranges
  • 4 1/2 digit resolution
  • AC coupled input
  • Priced competitively with less capable averaging AC meters
  • Peak value display
  • Green or red display
  • Optional dual relays, 4-20 mA & 0-10 V analog output, RS-232/485 I/O, parallel BCD output, low voltage AC & DC power.
  • 2, 20, 200 mA & 5 A ranges
  • 99.9% accuracy of full scale
  • Crest factor of 2.4 at full scale
  • Scalable for direct readout of external current shunts or current transformers
  • 85-264 Vac and 90-370 Vdc power standard
  • NEMA 4X, 1/8 DIN case
  • Certified to UL 3101-1, CAN/CSA-C22.2, EN 61010-1 (CE Mark).
The Laureate™ True AC RMS digital panel meter offers a high accuracy 4 1/2 digit display for five voltage ranges and four current ranges. It is suited for AC applications where there is considerable distortion of current waveforms from nonlinear loading. The input is AC coupled to read only the AC component, such as ripple on a power supply.

The True RMS AC digital panel meters use precision circuitry to compute the root-mean-square of complex waveforms from 10 Hz to 10 kHz. Spikes up to 2.4 times the maximum of each range are accurately measured. This provides a crest factor (Vp / Vrms) of 240 for a signal amplitude of 1% of full scale, decreasing to 2.4 at 100% of full scale.

High common mode rejection allows stable readings with current shunts located on the high side of the line. Five amp input capability allows the output of 5 A current transformers to be applied directly to the meter, with no need for a stepdown transformer. The current reading can easily be scaled to display the input to the current transformer. Digital scaling and calibration eliminate zero and span drift associated with potentiometers in non-microcomputer based meters.
High Accuracy
The typical accuracy is 99.9% of full scale, decreasing to 99.8% for low frequency at high amplitude, or high frequency at low amplitude. The above graph shows that maximum error is 0.1% of full scale over all frequency ranges of interest to AC power measurement. Error increases to 0.2%, represented by the two shaded areas, at low frequency and high amplitude, or high frequency and low amplitude.

Crest factor increases in inverse proportion to signal amplitude. As shown on the same graph, the maximum crest factor (Vp / Vrms) is 2.4x at full-scale amplitude, increasing to 240 at 1% of full-scale amplitude.

The Laureate True RMS AC ammeter utilizes the same high-speed analog-to-digital conversion method as all other Laureate digital panel meters. However, the meter settling time and control response to a step change in AC amplitude are limited by the True RMS AC converter circuit to approximately 1 second.
Interface Options
Plug-in isolated analog output, dual setpoint controller, and RS-232, RS-485 communications or BCD output boards can upgrade the digital panel meter from a simple monitor to system interface and control.
Built-in Flexibility & Safety
Laurel AC ammeters may be powered from 85-264 Vac and 90-370 Vdc, or optionally from 8-28 Vac and 9-37 Vdc. They are available with red or green LEDs. They are housed in a 1/8 DIN case that meets NEMA 4X (IP65) specifications from the front when panel mounted. Any setup functions and front panel keys may be locked out for simplified usage and security.


AC Voltage (1% to 100% of full scale) AC Voltage Range Resolution Input Ohms Typ Error at 25°C
200.00 mV
10 µV
22 M
0.1% FS
± count,
10 Hz to 10 kHz
2.000 V 100 µV
22 M
20.000 V
1 mV
1 M
200.00 V 10 mV
1 M
660.0 V 100 mV 1 M
AC Current (1% to 100% of full scale) AC Voltage Range Resolution Input Ohms Typ Error at 25°C
2.0000 mA 0.1 µA 100
0.1% FS
± count,
10 Hz to 10 kHz
20.000 mA 1.0 µA
200.00 mA
10 µA
5.000 A 1.0 mA 0.01  

AC Voltage & Current

Accuracy Maximum Signal
Span Tempco 0.0015% of reading/°C
Max applied
660 Vac for 20, 200 and 600 V ranges, 125 Vac for other
Zero Tempco 0.1 µV/°C Overcurrent
25x for 2 mA, 8x for 20 mA, 2.5x for 200 mA, 1x for 5 A
Crest Factor 2.4x at 100% of full scale ----- -----
Response Time Display
RMS to DC 1 s conversion settling time Readout 5 digits, 7-segment, 14.2 mm (.56")
A-to-D Rate 60/s at 60 Hz, 50/s at 50 Hz Color Red or green LED
Output Update 56/s at 60 Hz, 47/s at 50 Hz Range -99999 to +99999 or -99990 to +99990 (count by 10 with
Display Update 3.5/s at 60 Hz, 3/s at 50 Hz Indicators 2 red LED lamps
Power Excitation Output
Voltage, std 85-264 Vac and 90-370 Vdc 5 Vdc 5 Vdc ±5%, 100 mA max
Voltage, opt 8-28 Vac and 9-37 Vdc 10 Vdc 10 Vdc ±5%, 120 mA max
Frequency DC or 49-440 Hz 24 Vdc 24 Vdc ±5%, 50 mA max
Power isolation Safety-rated to 250 Vac, meter ground to earth ground,
DC to 60 Hz, 4.2 kVp per High Voltage Test
Output isolation 50 Vdc to meter ground
Operating Temperature 0°C to 55°C
Storage Temperature -40°C to 85°C
Relative HumidityProtection NEMA-4X (IP-65) when panel mounted
Connector Pin Assignments
Why Measure AC Power?
Many AC loads, such as electrical motors, will only operate reliably if the AC line voltage and frequency are within specified tolerances. Otherwise permanent damage to expensive plant equipment may occur. Motor generators and UPS systems will only operate reliably with the load for which they are rated. Drops in line voltage or frequency may indicate an excessive load and the possibility of equipment damage.

Laureate meters and counters are low-cost means to instrument AC power lines with great accuracy:

AC RMS Voltmeter. Full-scale ranges of interest are 200.00 V with 10 mV resolution and 660.0 V with 100 mV resolution. True RMS capability allows the display of RMS voltage for non-sinusoidal waveshapes, such as square waves from a UPS.

AC RMS Ammeter. A built-in 5 A range can be used to display currents up to 5.000 A with 10 mA resolution, or to accept the output of 5 A current transformers. The 200.00 mV range can be used with external current shunts. With either transformers or shunts, scaling to the input current is easily accomplished via the meter's front panel pushbutton switches.

Frequency Meter. Inverse period is used to determine AC line frequency to six-figure accuracy (60.0000 or 50.0000) in a few line cycles plus 30 ms.

Phase Angle Meter. Two signals with identical periods are applied to Channels A and B of the Laureate phase angle meter. A display from -180º to +180º is obtained by timing the rising edge of one channel and the falling edge of the other channel. A resolution of 1º, 0.1º or 0.01º is selectable. Accuracy is .01% up to 100 Hz, .1% at 1 kHz, and 1% at 10 kHz.

Using Laureate Meters to Synchronize Motor Generators
Successful synchronization of two motor generators requires that the voltage outputs of the generators be close to each other, that the two frequencies be identical, and that the voltage waveshapes be in phase.

The two voltages can be measured by two Laureate AC RMS Voltmeters, which offer 200.00 V and 660.0 V ranges. Or a single meter can be multiplexed by using an external toggle switch.

The two frequencies can be measured to six-figure accuracy by a single Laureate Dual Channel Counter, where each channel monitors a generator. The two AC neutrals must be tied to meter ground. Pressing a front-panel key toggles the reading between the channels.

Phase angle can be measured using the Laureate Dual Channel Counter.

5672 Bolsa Avenue Huntington Beach, CA 92649 - USA - Ph (714) 622-2000 - Fax (714) 622-2001