Laureate™ True  RMS Voltage & Current
Meter with 1 Cycle Update at 50/60 Hz
200 mV - 600 V and 2 mA - 5 A full-scale ranges

• True AC RMS measurement with crest factor of 3.0 at FS
• Fast response: reading 0-16.7 ms after completion of each
  input signal cycle.
• 0.1% accuracy, 0% to 100% of span, 10 Hz to 10 kHz
• Reads AC only or AC plus DC
• 0.2, 2, 20, 200 & 600V voltage ranges with 132% overrange
• 2, 20, 200 mA & 5A current ranges with 132% overrange
• All ranges factory calibrated
• Display flashes at 132% overrange
• Scalable to 5 digits for external current shunts or 5A current transformers
• Selectable peak or valley display
• 85-264 Vac universal AC power
• Green or red display
• NEMA 4X, 1/8 DIN case
• Certified to UL 61010C-1 (UL mark), EN 61010-1 (CE mark)
• RoHS compliant
• Priced competitively with less capable AC meters
  Options:
• Low voltage power: 10-48 Vdc or 12-32 Vac
• 2 or 4 output relays, contact or solid state
• Isolated analog output: 4-20 mA, 0-20 mA, 0-10V, 10 to +10V
• Serial communications: RS232, RS485, Modbus RS485, USB, USB-to-RS485 converter

The Laureate™ True RMS meter is a 60,000 count digital panel meter with exceptional performance at half the price of a bench top meter. It can measure true RMS voltage or current of AC signals where there is considerable distortion of the waveform, such as rectifier outputs or waveforms chopped by an SCR, TRIAC or transistor circuit, as illustrated.

True RMS readings in 0-16 ms after completion of one input signal cycle allow anomalies to be detected and alarmed before they become expensive problems. Fast on/off control and alarm can be achieved with optional dual or quad relays, either contact or solid state. The meter can also capture peak and valley readings that occur at the nominal rate of 50/60 Hz.

Accurate is 0.1% of full scale for signals from DC to 10 kHz and signal amplitudes down to 0. The crest factor (Vp / Vrms) is 3.0 at full-scale Vrms of 20,000 counts and a Vp of 60,000 counts. The meter starts to flash overrange at 132% of full scale Vrms , at which point the available crest factor is 60,000 / 26,400 = 2.27. Meaningful readings with rated resolution continue to be obtained up to 212% of full scale Vrms (42,433 counts) for sinusoidal signals, at which point the available crest factor is 1.414. For safety reasons, the maximum RMS input signal should never exceed 600V or 5A. UL certification is for a maximum voltage of 300 Vrms.

AC or DC coupling is jumper selectable on the signal conditioner board. AC coupling accommodates signals from 10 Hz to 10 kHz and is suitable for applications such as measuring AC ripple on a DC power supply. DC coupling accommodates signals from 0 to 10 kHz. Multiple integral cycles are averaged for signals above 50/60 Hz. A single cycle is captured for signals from 3 Hz to 50/60 Hz. Below 3 Hz and at DC, the capture rate is 3/sec.

Use with current Transformers. 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 5A current transformers to be applied directly to the meter, with no need for a stepdown transformer. The meter reading can easily be scaled for the current transformer ratio. Digital scaling and calibration eliminate zero and span drift associated with potentiometers in non-microcomputer based meters. Digital filtering is selectable for noisy signals.

Designed for flexibility. An isolated sensor excitation output is standard. Optional plug-in boards for communications and control include an analog output board, dual or quad relay boards, and serial communications boards. Laureate meters may be powered from 85-264 Vac or optionally from 12-32 Vac or 10-48 Vdc. The display is available with red or green LEDs. The 1/8 DIN case meets NEMA 4X (IP65) specifications from the front when panel mounted. Any setup functions and front panel keys can be locked out for simplified usage and security.

Specifications

AC Voltage (0 to 100% of full scale range)

Using Laureate Meters and Counters to Instrument an AC Line

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. 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 and alarm AC power lines with great accuracy:

• AC RMS Voltmeter and Ammeter, as documented in this page. True RMS capability allows the display of RMS voltage for non-sinusoidal waveshapes, such as square waves from a UPS. A built-in 5 A range can be used to display currents up to 5.000 A with 1 mA resolution or  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 of 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 & Power Factor Meter. Two signals with identical periods are applied to Channels A and B. A phase angle 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.

Application Example
Using Laureate Meters to Synchronize Two 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 600.0 V ranges. Or a single meter can be multiplexed by using an external toggle switch.
   
• Two frequencies A & B 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. The meter can also display frequency A - frequency B, or frequency A / frequency B without toggling.
   

• Phase angle can be measured using the Laureate Phase Meter.