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Standard Features
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Description
The Micron Weight Meter is compact and inexpensive, yet extremely accurate and capable. It is available with the Micron load cell or DC signal conditioner board.
The DC signal conditioner board can accept preconditioned process signals such as 0-10V, 1-5V or 4-20 mA, full-scale DC signals from 200 mV to 660V or 2 mA to 5A, or load cell signals down to 200 mV full scale. With this board, a 20 mV strain gauge output can be scaled to display up to 10,000 counts, while a 200 mV output can be scaled to display up to 99,999 counts. 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 accuracy of actual load cells near the low and high ends of their ranges. Custom curve linearization also allows high accuracy readings to be achieved with lower cost, less linear load cells. Display & Setpoint Functions for Weighing Application
Easy scale calibration is achieved using a simple two-point calibration method. First, the desired LO IN reading is set to 0, and the desired HI IN reading is set to a desired value. With no weight on the scale, a button is pushed for LO IN. With a known weight on the scale, that button is pushed again for HI IN. The meter then automatically computes scale and offset for readout up to five digits in weight units. Extremely fast read rates are provided for weigh-in-motion systems, setpoint control, and computer interface. Concurrent Slope (Pat 5,262,780) is a method of analog-to-digital conversion which allows up to 60 conversions per second while integrating the input signal over a full AC line cycle. An adaptive digital filter can be set for time constants from 17 ms to 9 s, yet responds rapidly to a change in input signal level exceeding a threshold value. The meter can also automatically select the best filter setting for maximum noise rejection and minimum response time. Peak and valley capture are standard. 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. |
With Load Cell Signal Conditioner
Full-Scale Input, mV |
Zero Adjust |
Span Adjust |
Error at 25°C |
±20.000 ±50.000 ±100.00 ±250.00 ±500.00 |
-99,999 to +99,999 |
0 to ±99,999 |
0.0030% of reading /°C |
With DC Signal Conditioner
Full-Scale Input |
Zero Adjust |
Span Adjust |
Error at 25°C |
±200 mV ±2 V ±20 V ±20 mA |
-99,999 to +99,999 |
0 to ±99,999 |
0.01% FS ±2 counts |
With Load Cell or DC Signal Conditioner
Display |
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Readout Range Rounding Indicators |
5 LED digits, 7-segment, 14.2 mm (.56"), red or green -99999 to +99999 -999990 to +999990 (with fixed selectable right-hand zero) Count by 1, 2, 5, 10, 20, 50, 100 Four LED lamps |
Accuracy |
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Error at 25°C Span Tempco Zero Tempco Calibration Method Load Cell Linearization |
0.01% FS ± 2 counts 0.0015% of reading/°C Auto-zero 2 points using zero weight and known weight Provided by Extended meter version |
Noise Rejection |
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CMR, DC to 60 Hz NMR at 50/60 Hz |
130 dB 90 dB with min filtering |
A-to-D Conversion |
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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 |
Power |
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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) |
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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) |
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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 |
Relay Outputs (optional) |
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Relay Types Current Ratings Output common Isolation |
Two Form C contact relays, SPDT Two Form A, AC/DC solid state relays, SPST (NO) 8A at 250 Vac or 24 Vdc for contact relays 130 mA at 140 Vac or 180 Vdc for solid state relays Isolated commons for dual relays or each pair of quad relays 250V rms working, 2.3 kV rms per 1 min test |
Serial Data I/O (optional) |
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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 |
Environmental |
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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 |
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The five-digit meter can be scaled to display truck weight up to 99,999 lbs with 1 lb resolution or 999,990 lbs with 10 lb resolution. Accuracy is 0.01% of full scale at 25ºC. To avoid the effects of system-level noise, different filter settings as well as "count by" of 1, 2, 5, 10, 20, 50 or 100 with rounding are selectable. To read out net weight of the load, the truck can first be weighed empty, and this weight can be entered as tare at the push of a button in an auto-tare mode. Or the nominal tare value of the truck can be entered manually. Display of net weight or gross weight is at the push of a button. The gross weight and net weight can be alarmed, be transmitted to a computer via RS232 or RS485, or be transmitted via a 4-20 mA analog signal. |
Electrical Connections & Setpoint Offset
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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. |
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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. |
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The DC signal conditioner board can be utilized to accept preconditioned 4-20 mA or 0-10 V scale signals. In two-wire 4-20 mA transmitter connection, the same two wires are used to apply voltage and carry the output current. |
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In a repetitive fill operation (as illustrated by example), a setpoint offset of -50 will allow a shutoff setpoint to be set for 1000 and actual shutoff to occur at 950 if it is known that 50 units will still flow following shutoff. An offset can also be applied to emptying operations. |
The load cell signal conditioner board, which is normally used with the weight meter, accepts full-scale ranges of 20, 50, 100, 250 and 500 mV with 4- or 6-wire load cell hookup to display up to 99,999 counts. With 4-wire hookup, the meter operates in a ratiometric mode to eliminate errors due to supply variations. With 6-wire hookup, it also compensates for variations in transducer lead resistance, thereby allowing long cable runs in changing temperature environments. The built-in, isolated excitation supply can power up to four 350-ohm load cells in parallel at 10 Vdc.
The Micron weight meter power all four 350 ohm load cells of the scale with its 10 V, 120 mA isolated excitation output. Six-wire connection eliminates the effects of lead resistance and allows long cable runs from the control room to the scale.
