Micron Meters- Process, Strain and Potentiometer Follower Meter

Description

Micron digital process and strain panel meters are a cost-effective solution to monitoring and control applications which require zero and span adjustment for process signals such such as 4-20 mA, 0-5 V, 0-10 V, or strain gauges. The meters are also suitable for potentiometer follower applications, where the transducer output is a changing resistance.

The display is scalable to five full digits from -99,999 to +99,999 from the front panel to read directly in engineering units, such as PSI. Three scaling methods are selectable: scale and offset, two-point method, and system-level calibration using actual transducer signals. All ranges are precalibrated at the factory, so that recalibration is not needed when changing ranges or signal conditioners.

Strain gauges with a 20 mV output can be scaled to display up to 10,000 counts with a 4-wire ratiometric connection, while 200 mV outputs of can be scaled to display up to 99,999 counts. For higher sensitivity, 20 mV signals can be scaled to 99,999 counts with a 4- or 6-wire connection using the Micron load cell meter.

Signal conditioner for Laureate digital panel meter for process, strain, and potentiometer follower applications An isolated 5, 10 or 24 Vdc isolated excitation output is standard to power external transducers and transmitters. Up to 120 mA is provided at 10V to power four 350 ohm load cells in parallel. When powering strain gauges, load cells or potentiometers, the excitation output is monitored by the meter to eliminate errors due to voltage variations.

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.

Auto-tare allows the display to be zeroed for any input signal by applying a switch closure or logic signal at the rear connector. The tare value is stored in non-volatile memory and is retained when power is removed.

An Extended Micron computer board can display rate based on successive readings. It also allows exceptionally accurate custom curve linearization, for example to read out liquid volume or rate of flow in a horizontal cylindrical tank based on level reported by a 4-20 mA transmitter. For setup, up to 180 data points can be input into a computer spreadsheet or text file by the user. The computer then calculates spline-fit segments, which are downloaded into the 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.

SPECIFICATIONS

DC Voltage

DC Voltage Range	Resolution	Input Ohms	Error at 25°C ±2 counts
±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	1 G 1 G 10 M 10 M 10 M 10 M	0.01% FS 0.01% FS 0.01% FS 0.01% FS 0.02% FS 0.02% FS

DC Current

DC Current Range	Resolution	Input Ohms	Error at 25°C ±2 counts
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	0.01% FS 0.01% FS 0.01% FS 0.04% FS

DC 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) Minus sign, 2 red LED lamps
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
Accuracy
Error at 25°C Span Tempco Zero Tempco	0.01% FS ± 2 counts (except 5A range) 0.003% of reading/°C 0.1 count/°C
Noise Rejection
CMR, DC to 60 Hz NMR at 50/60 Hz	130 dB 90 dB with min filtering
Maximum Signal
Max applied voltage Current protection	600 Vac for 20, 200 & 600 V 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	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

Application Examples

Wiring a Laureate digital panel meter for a potentiometric pot follower application

Potentiometer Application

In potentiometric (or potentiometer follower) applications, the signal from a sliding contact voltage divider can be converted to engineering units such as position, level or percentage. By operating in a ratiometric mode, the meter will remove any effects caused by variations in the excitation supply.

For use with a 1 kohm potentiometer, the recommended applied excitation voltage is 10 V, and a 2 kohm resistor should be placed in series with the excitation output and excitation return leads. This will allow the meter's 2.0000 V scale with a high input impedance of 1 Gohm to be used.


Powering two-wire transmitters The isolated 24 Vdc, 50 mA excitation output, which is standard with all Micron meters, is ideal for powering two-wire, 4-20 mA transmitters. The same two wires are used to apply voltage and carry the output current. Inside the meter, the 4-20 mA current is dropped across a 10 ohm resistor and sets up a 40-200 mV voltage, which is then sensed by the meter and scaled to engineering units.	Testing with peak detection Destructive testing is an ideal application for the Micron strain meter. Peak readings are automatically captured at rates up to 60 per second, while the display updates at a legible 3.5 readings per second. The peak reading can be recalled at the push of a button or be transmitted via RS-232 or RS-485. The meter provides isolated 10 Vdc power for up to four (4) the strain gauges and can be scaled to read out directly in engineering units from -99,999 to +99,999.

Custom curve linearization The Micron DC meter with the Extended main board option allows exceptionally accurate custom curve linearization. For setup, up to 180 data points can be entered into a spreadsheet. The system then creates multiple non-linear spline-fit segments, which provide much better accuracy than linear segments. Illustrated, is the readout of volume of irregularly shaped tanks based on measured liquid level or pressure. Altimeters and thermistors are further applications.	Rate from successive readings The Extended computer board allows the display of rate based on successive readings, for instance flow rate based on changes in liquid level or static pressure in a tank. In the above illustration, the meter displays the rate in gallons at which a horizontal tank is being emptied. The input to the meter can be nonlinear, since only the linearized readings are compared for the determination of rate.