Laureate™ True AC RMS Voltage
& Current Panel Meters
0.2 V - 600 V and 2 mA - 5 A full-scale ranges

Features

• 0.2, 2, 20, 200 & 600 V ranges
• 2, 20, 200 mA & 5 A ranges
• 4 1/2 digit resolution
• 99.9% accuracy of full scale
• AC coupled input
• Crest factor of 2.4 at full scale
• Priced competitively with less capable averaging AC meters
• Scalable for direct readout of external current shunts or current transformers
• Peak value display
• 95-240 Vac ±10% or 90-300 Vdc power standard
• Green or red display
• NEMA 4X, 1/8 DIN case
• Dual relay option
• Analog output option
• Serial communication options
• Low voltage AC & DC power
• Certified to UL 61010C-1 (UL mark), EN 61010-1 (CE mark), and RoHS.

The Laureate™ True RMS 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 meter uses 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.

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 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

Maximum error as a function of frequency and signal amplitude

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 RMS meter utilizes the same high-speed analog-to-digital conversion method as all other Laureate panel meters. However, the meter settling time and control response to a step change in AC amplitude are limited by the RMS converter circuit to approximately 1 second.

Interface Options

Plug-in isolated analog output, dual setpoint controller, or RS-232/485 communications, can upgrade the Laureate from a simple monitor to system interface and control.

Built-in Flexibility & Safety

Laureates may be powered from 95-240 Vac ±10% or 90-300 Vdc, or optionally from 12-30 Vac or 10-48 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.

Specifications

AC Voltage (1% to 100% of full scale)

AC Voltage Range	Resolution	Input Ohms	Typ Error at 25°C 10 Hz to 10 kHz
200.00 mV 2.000 V 20.000 V 200.00 V   600.0 V * 300.0 V	10 µV 100 µV 1 mV 10 mV 100 mV 100 mV	22 M 22 M 1 M 1 M 1 M 1 M	0.15% FS 0.15% FS 0.15% FS 0.15% FS 0.15% FS 0.15% FS

* Range does not include U/L certification.

AC Current (1% to 100% of full scale)

AC Current Range	Resolution	Input Ohms	Typ Error at 25°C 10 Hz to 10 kHz
2.0000 mA 20.000 mA 200.00 mA 5.000 A	0.1 µA 1.0 µA 10 µA 1.0 mA	100 10 1 0.01	0.15% FS 0.15% FS 0.15% FS 0.25% FS

Both AC Voltage & Current

Display
Readout Range Indicators	5 LED digits, 7-segment, 14.2 mm (.56"), red or green -99999 to 99999 or -99990 to 99990 (count by 10 with rounding) 2 red LED lamps
Accuracy
Span Tempco Zero Tempco Crest Factor	0.005% of reading/°C 0.1 count/°C 2.4x at 100% of full scale
Response Time
RMS to DC A-to-D rate Output Update Display Update	1 s conversion settling time 60/s at 60 Hz, 50/s at 50 Hz 56/s at 60 Hz, 47/s at 50 Hz 3.5/s at 60 Hz, 3/s at 50 Hz
Maximum Signal
Max applied voltage Over-current protection	600 Vac for 20, 200, 600V ranges, 125 Vac other ranges 25x for 2 mA, 8x for 20 mA, 2.5x for 200 mA, 1x for 5 A
Power
Voltage, standard Voltage, optional Frequency Power Isolation	95-240 Vac ±10% or 90-300 Vdc 12-30 Vac or 10-48 Vdc DC or 47-63 Hz 250V rms working, 2.3 kV rms per 1 min test
Excitation Output (standard)
5 Vdc 10 Vdc 24 Vdc Output isolation	5 Vdc ±5%, 100 mA 10 Vdc ±5%, 120 mA 24 Vdc ±5%, 50 mA 50 Vdc to meter ground
Analog Output (optional)
Output levels Compliance Scaling Resolution Isolation	0-10V, 0-20 mA, 4-20 mA (jumper selectable) 2 mA at 10V (5 kOhm load), 12V at 20 mA (0-60 ohm load) Zero and full scale adjustable from -99999 to +99999 12 bits (0.025% of full scale) 250V rms working, 2.3 kV rms per 1 min test
Dual Contact Relay Outputs (optional)
Relay Type Load Rating Isolation	Form C 8A at 250 Vac or 24 Vdc 250V rms working, 2.3 kV rms per 1 min test
Dual Solid State Relay Outputs (optional)
Relay Type Load Rating Isolation	SPST, normally open, Form A 120 mA at 130 Vac or 170 Vdc, 28 ohms series resistance. 250V rms working, 2.3 kV rms per 1 min test
Serial Data I/O (optional)
Board Selections Protocols Data Rates Digital Addresses Isolation	RS232, RS485, Modbus RS485 Modbus RTU, Modbus ASCII, simpler Laurel ASCII 300 to 19200 bps 247 (Modbus), 31 (Laurel ASCII), 250V rms working, 2.3 kV rms per 1 min test
Signal Connections
Environmental
Operating Temperature Storage Temperature Relative Humidity Protection	0°C to 60°C -40°C to 85°C 95% at 40°C, non-condensing NEMA-4X (IP-65) when panel mounted

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. 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 600.0 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 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.
   
• 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 Phase Meter.

Note: The same AC RMS signal conditioner can be user configured for AC Volts or AC Amps. It is precalibrated in EEPROM for all AC Volt and AC Amp ranges listed.