Electro-Numerics, Inc.
42213 Sarah Way, Temecula, CA 92590, USA

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Tel: 800-854-8530 (USA)
Tel: 951-699-2437 
Fax: 951-695-7246

sales@electronumerics.com

    Micro Series Load Cell & Microvolt
Digital Panel Meters

20 mV - 500 mV full-scale ranges, 4- or 6-wire connection
 

  
Features

  • Available in three digit heights: 0.56" for panel mounting, 1.0" (Mighty-1) or 5.0" (Mighty-5) for long-distance viewing.
  • 20, 50, 100, 250 & 500 mV ranges.
  • 5-digit resolution with span from 0 to 99,999
  • Zero from -99,999 to +99,999
  • Selectable fixed right-hand zero.
  • Isolated 10 Vdc supply to power up to four 350-ohm load cells in parallel.
  • 4- or 6-wire hookup to eliminate lead resistance errors.
  • Ratiometric operation to cancel variations in excitation supply.
  • Up to 60 conversions per second.
  • Peak and valley value display (standard).
  • Auto-tare with tare value stored in memory.
  • AC or DC powered.
  • Green or red display.
  • Choice of isolated plug-in options for control and computer interface:
    dual relays, 4-20 mA & 0-10 V analog output, RS232/485 serial I/O, low voltage AC & DC power.
  • 1/8 DIN case environmentally sealed to NEMA-4X from front panel.
  • 1/8 DIN version certified to UL 3101-1, CAN/CSA-C22.2, EN 61010-1 (CE Mark).

Description

Load cell signal conditioner board for Laureate digital panel meterThe Micro Series load cell and microvoltmeter is a high-sensitivity monitor and controller for use with load cells, strain gauges and microvolt input signals where high accuracy and stability are required.

Usage as a DC microvoltmeter provides sensitivity down to 20 mV full scale with 1 V resolution. With a digital multiplier of five, 99,999 counts can be displayed with a sensitivity of 0.2 V per count. A moving average filter with a time constant of 1.2 sec or greater should then be selected.

Usage as a load cell meter allows six-wire hookup and scaling for direct readout in engineering units, such as pounds, kilograms or PSI. Scaling can be via front panel pushbuttons or a computer. Zero may be set from -99,999 to +99,999. Range may be scaled from 0 to 99,999. Digital scaling and calibration eliminate drift caused by potentiometers in non-microcomputer based meters.

Built-in Excitation

An isolated 10 Vdc excitation supply can provide up to 120 mA of current to power up to four 350-ohm load cells in parallel. The meter operates in a ratiometric mode to eliminate errors due to supply variations. When excitation sense inputs are used in 6-wire connection, the meter compensates for variation in resistance of the transducer leads, thereby allowing long cable runs.

Fast Read Rate plus Peak Capture

Micro Series meters use Concurrent Slope (Pat 5,262,780) analog-to-digital conversion, which allows up to 60 conversions per second, while integrating the signal over a full power cycle. High read rate is ideal for peak value capture and for real-time computer interface and control. Peak capture is standard.

Selectable Signal Filtering

The displayed readings and the data outputs can be separately selected to be either unfiltered or filtered.

  • An unfiltered selection updates after each conversion for fastest response, up to 60/sec, while integrating the input signal over a full power cycle. Fast read rate provides true peak readings and aids in control applications.
  • A batch average filter selection averages each 16 conversions for an update every 1/4 sec.
  • An adaptive moving average filter selection provides a choice of 8 time constants from 80 ms to 9.6 s. When a significant change in signal level occurs, the filter adapts by briefly switching to the shortest time to follow the change, then reverts back to its selected time constant. Another choice is Auto, which provides an automatic time constant selection based on the signal noise characteristics.

Easy Scaling

Micro Series DC, process and load cell meters allow easy setting of scale and offset by either of two methods.

  • With the coordinate reading method, the meter reads the high and low signal values, and the user enters the desired high an low reading values. The meter then calculates the span multiplier and offset. This method is ideal if an external calibration reference is available.
  • With the manual coordinate method, the user enters the high and low input values in Volts plus the desired high and low reading values. This method is suitable if an no external calibration reference is available.

Auto-tare

For weighing applications, auto-tare is standard. Auto-tare can set the displayed value to zero to subtract the weight of an empty container. Auto-tare may be controlled by an external pushbutton contact closure or logic signal through an input on the power supply connector. The tare value is stored in memory. Additional capabilities for weighing applications are provided by the Micro weight / scale meter, as described in a separate web page.

Other Features and Options

Plug-in isolated analog output, dual-setpoint controller, and RS232/485 serial communications boards can upgrade Micro an Mighty Series load cell meters from stand-alone monitor to system interface and control. With the optional analog output board, the meter can serve as a 0-10 V or 4-20 mA transmitter.

Micro Series instruments can be powered from 95-240 Vac 10% and 95-370 Vdc, or optionally from 12-34 Vac and 10-48 Vdc. Any setup functions and front panel keys may be locked out for simplified usage and security. The popular 1/8 DIN version with 0.56" high digits is environmentally sealed to NEMA-4X (IP65) from the front when panel mounted, and is available with red or green LEDs.

Specifications

DC Microvoltmeter Inputs
  
Input Range
mV
Resolution Error at 25C
20.000
50.000
100.00
250.00
500.00
1.0 V
2.5 V
5.0 V
12.5 V
25 V
0.01% FS
1 count

Load Cell Inputs

Full-Scale
Input, mV
Zero
Adjust
Span
Adjust
Error at 25C
20.000
50.000
100.00
250.00
500.00
-99,999
to
+99,999
0 to
99,999
0.01% FS
1 count

DC Microvolts & Load Cell

Accuracy
Span Tempco
Zero Tempco
0.0015% of reading/C
0.1 V/C
Noise Rejection
CMR, DC to 60 Hz
NMR at 50/60 Hz
130 dB
90 dB with min filtering
A-to-D Conversion
Technique
A-to-D Rate
Output Update
Display Update
Concurrent Slope(Pat 5,262,780)
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
Display
Readout
Digit Height
Color
Range
  
Indicators
5 digits, 7-segment
Available with 0.56", 1.0", 4.0" or 5.0" digits.
High brightness red. Green available with 0.56" digits.
-99999 to +99999 or -99990 to +99990
(count by 10 with rounding)
Minus sign, 2 red LED lamps
Power
Voltage, std.
Voltage, opt.
Frequency
Power isolation
95-240 Vac 10% and 95-370 Vdc
12-34 Vac and 10-48 Vdc
DC or 49-440 Hz
Safety-rated to 250 Vac, meter ground to earth ground,
DC to 60 Hz, 4.2 kVp per High Voltage Test
Excitation Output
5 Vdc
10 Vdc
24 Vdc
Output isolation
5 Vdc 5%, 100 mA max
10 Vdc 5%, 120 mA max
24 Vdc 5%, 50 mA max
50 Vdc to meter ground
Environmental
Operating Temperature
Storage Temperature
Relative Humidity
Protection
0C to 60C
-40C to 85C
95% at 40C, non-condensing
NEMA-4X (IP-65) when panel mounted

Load Cell Meter Connections
  

4-wire digital panel meter load cell bridge connection

In 4-wire connection, the excitation and sense lines are tied together. The meter can make ratiometric corrections for supply voltage variations, but not compensate for variations in lead resistance. This connection is often used with short cable runs.

6-wire digital panel meter load cell bridge connection

In 6-wire connection, the sense lines are separate from the excitation lines, thereby eliminating effects due to variations in lead resistance. This allows long cable runs in outdoor environments with temperature extremes.

Up to six 350-ohm load cell bridges connected in parallel to Laureate digital panel meter

For large scales, up to four 350 ohm load cells can be powered by a single Micro load cell meter, whose excitation output is rated 120 mA at 10 V. The excitation and sense points of the four bridges are connected in parallel through a summing box.

Sample Load Cell Meter Applications
  
Auto tare function of load cell meter Auto-Tare

To read the net weight of an object, the empty container is first weighed, and an external button is pushed to zero out the display. The meter will then read net weight when an object is added to the empty container. The tare value is stored in memory for subsequent readings.

Determining tank volume with a load cell panel meter Determining Volume Using Load Cells

An easy way to determine volume of an irregularly shaped tank with no need for linearizing is to weigh the tank using load cells. The meter will automatic- ally tare out the weight of the empty tank and then scale the load cell signals to units of volume, such as gallons.

Using a digital panel meter with peak capture for testing tensile strength Peak Capture for Testing the Tensile Strength of Wire

Peak readings are automatically captured at rates up to 60 per second, while the display updates at a legible 3.5 per second. The peak reading can be recalled at the push of a button or be always displayed. It can also be transmitted to a computer via RS232 or RS485.

Micro & Mighty Series Downloads

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