Micron Load Cell & Microvolt
Digital Panel Meter

• 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 with rounding
• Isolated 10 Vdc supply to power up to four 350-ohm load cells in parallel
• 4- or 6-wire hookup to avoid lead resistance effects
• Ratiometric operation to cancel variations in excitation supply
• Up to 60 conversions per second
• Peak or valley display
• Auto-tare with tare value stored in memory
• External controls for reset, meter hold, decimal points, and tare
• Universal AC power, 85-264 Vac
• NEMA 4X, 1/8 DIN case
  Options:
• Low voltage power: 10-48 Vdc or 12-30 Vac
• Dual or Quad relays: Form C contact or Form A solid state
• Analog output: Isolated, 4-20 mA, 0-20 mA, 0-10V, -10 to +10V
• Serial communications: RS232, RS485, Modbus RS485, USB, USB-to-RS485 converter
• Certified to UL 61010C-1 (UL mark), EN 61010-1 (CE mark), and RoHS).

Description

The Micron load cell & microvolt meter 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.

• DC microvoltmeter operation provides sensitivity down to 20 mV full scale with 1 µV resolution. A display span of 99,999 counts with sensitivity of 0.2 µV per count can be obtained by applying a digital multiplier of five. A moving average digital filter assures quiet readings in electrically noisy environments.
   
• Load cell operation 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.

Meter accuracy is 0.01% of full scale ± 2 counts with an ideal load cell. Custom curve linearization, which is available with the optional Extended main board, can extend the working range of real-world load cells. Custom curve linearization also allows high accuracy to be achieved with lower cost, less linear load cells.

An built-in isolated 10 Vdc excitation supply can provide up to 120 mA of current at 10V to power 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.

High read rates at up to 60 or 50 conversions per second while integrating the signal over a full power cycle are provided by Concurrent Slope (US Pat 5,262,780) analog-to-digital conversion. High read rates are ideal for peak or valley capture, real-time computer interface, and control.

Peak and valley values are automatically captured. These may be displayed via a front panel pushbutton command or control signal at the rear connector, or be transmitted as serial data.

Digital filtering is selectable for electrically noisy environments, including a batch averaging filter and an adaptive moving average filter which provides a choice of 8 time constants from 80 ms to 9.6 s. When a significant change in signal level occurs, that filter adapts by briefly switching to the shortest time to follow the change, then reverts back to the selected time constant. In a selectable Auto filter mode, the filter time constant is automatically selected based on detected signal noise.

Easy scale and offset are provided by Micron DC, process and load cell meters by either of two selectable 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 no external calibration reference is available.

Auto-tare is standard for weighing applications to subtract the weight of an empty container and may be controlled by an external pushbutton contact closure or a logic signal. Additional capabilities for weighing applications are provided by the Micron weight & scale meter.

Designed for flexibility. Plug-in isolated analog output, dual or quad setpoint controller, and serial communications boards can upgrade Microns from a simple monitor to system interface and control. Microns may be powered from 85-264 Vac or optionally from 12-30 Vac or 10-48 Vdc. They are 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.

Load Cell Inputs

DC Microvolts & Load Cell

Accuracy
Error at 25°C Span Tempco Zero Tempco Load Cell Linearization	0.01% FS ± 2 counts 0.0015% of reading/°C 0.1 µV/°C Provided by Extended meter version
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 Range Indicators	5 LED digits, 7-segment, 14.2 mm (.56"), red or green. -99999 to 99999 or -99990 to 99990 (count by 10) Minus sign, 2 red LED lamps
Power
Voltage, standard Voltage, optional Frequency Power Isolation	85-264 Vac or 90-300 Vdc (DC operation not UL approved) 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 Current compliance Voltage compliance Scaling Resolution Isolation	4-20 mA, 0-20 mA, 0-10V, -10 to +10V (jumper selectable) 2 mA at 10V ( > 5 kOhm load) 12V at 20 mA ( < 600 Ohm load) Zero and full scale adjustable from -99999 to +99999 16 bits (0.0015% of full scale) 250V rms working, 2.3 kV rms per 1 min test
Dual or  Quad Contact Relay Outputs (optional)
Relay Type Load Rating Isolation	Form C, SPDT 8A at 250 Vac or 24 Vdc 250V rms working, 2.3 kV rms per 1 min test
Dual or Quad Solid State Relay Outputs (optional)
Relay Type Load Rating Isolation	Form A, SPST, normally open 130 mA at 140 Vac or 180 Vdc 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, USB, USB-to-RS485 converter Modbus RTU, Modbus ASCII, simpler Micron ASCII 300 to 19200 bps 247 (Modbus), 31 (Micron ASCII), 250V rms working, 2.3 kV rms per 1 min test
Signal Connections
Environmental
Operating Temp. Storage Temp. 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

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.

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.

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 RS-232 or RS-485.