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MW50 Weight Meter
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Features
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Setpoint control with offset compensation for filling applications.
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5-digit resolution with scaling from 0 to 99,999.
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Auto-tare or manual tare, with tare value storage
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Auto-zero display function.
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Display toggle between gross or net weight.
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Count by 1, 2, 5, 10, 20, 50 or 100 with rounding.
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Easy scale calibration using known weight.
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10 Vdc Excitation for up to 4x350 ohm load cells.
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NEMA 4X front panel, 1/8 DIN case.
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Certified to UL 3101-1, EN 61010-1 (CE Mark).
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Description
The Weight Meter provides a choice of two signal conditioner boards: the load cell signal conditioner board, which provides full-scale ranges of 20, 50, 100, 250 and 500 mV with 4- or 6-wire load cell hookup, and the DC signal conditioner board, which allows the meter to accept preconditioned signals such as 0-10 V or 4-20 mA. Options include setpoint control, analog output and digital communication boards.
Display & Setpoint Functions
Setpoint Offset. The ON/OFF setpoint control action can be programmed to occur with a specified offset. For instance, if bags are to be filled to 100 lbs and the material delivery spout is known to hold and dispense an additional 2.5 lbs following shut-off, an offset of -2.5 lbs can be programmed. The setpoint can then be set to 100 lbs, and the filling valve will be automatically shut off when the measured weight reaches 97.5 lbs.
Count-by Function. The weight meter can be programmed so that the display is rounded off to multiples of 1, 2, 5, 10, 20, 50 or 100. For example, if count-by 10 is selected, the meter will display 20 for an internal count of 15 to 24.
Fixed Zero. The display can be shifted left to allow a fixed zero to be displayed to the right. This allows values up to 999,990 to be displayed.
Auto-zero Function. An auto-zero limit from 0 to 9 counts can be programmed to compensate for load cell drift. Whenever the meter comes to rest within that limit from zero, it will auto-zero. Entering 0 disables auto-zero.
Two Tare Functions. The weight meter offers two types of tare: auto-tare and manual tare. In auto-tare, an input line is grounded by an external pushbutton. This causes the current weight, which is normally the empty weight of the container to be stored in memory as an offset. In manual tare, the tare value can be entered manually via the front panel or a computer. For instance, the tare value may be the stated empty weight of a truck or rail car. Pressing the Reset button on the front panel toggles the display between gross weight (total weight on the scale) and net weight (gross weight with tare subtracted).
Load Cell Connection
The load cell signal conditioner, which is normally used with the weight meter, is designed for 4- or 6-wire hookup. In 4-wire hookup, the meter operates in a ratiometric mode to eliminate errors due to supply variations. In 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 10 Vdc excitation supply can power up to four 350-ohm load cells in parallel.
Easy Scale Calibration
The weight meter is normally set up 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.
Fast Response
The weight meter offers extremely fast read rates. These are ideal for weigh-in-motion systems, setpoint control, and computer interface applications. Concurrent Slope (Pat 5,262,780) is a method of analog-to-digital conversion that allows up to 60 conversions per second, while integrating the input signal over a full 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 automatically select the best filter setting for maximum noise rejection and minimum response time. Control and interface outputs can be derived from the filtered signal or, for quicker response, from the unfiltered signal. Display of peak value is standard in the series.
Add-on Functions & Options
Plug-in isolated analog output, dual setpoint controller, RS-232/485 communications, and parallel BCD output boards can upgrade the weight meter to system interface and control.
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Specifications
With Load Cell Signal Conditioner
Full-Scale
Input, mV
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Zero
Adjust
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Span
Adjust
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Error at 25°C
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±20.000
±50.000
±100.00
±250.00
±500.00
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-99,999
to
+99,999
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0 to
±99,999
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0.0030% of
reading /°C
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With DC Signal Conditioner
Full-Scale
Input
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Zero
Adjust
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Span
Adjust
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Error at 25°C
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±200 mV
±2 V
±20 V
±20 mA
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-99,999
to +99,999
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0 to
±99,999
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0.01% FS
±1 count
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With Load Cell or DC Signal Conditioners
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Accuracy, Load Cell Signal
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Span Tempco
Zero Tempco
Calibration Method
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0.0030% of reading/°C
Auto-zero
2 points using zero weight and known weight
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Accuracy, DC Signal
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Span Tempco
Zero Tempco
Calibration Method
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0.01% FS ±1 count
Auto-zero
2 points using zero weight and known weight
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Noise Rejection
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CMR, DC to 60 Hz
NMR at 50/60 Hz
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130 dB
90 dB with min filtering
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A-to-D Conversion
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Technique
A-to-D Rate
Output Update
Display Update
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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
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Display
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Readout
Color
Range
Rounding
Indicators
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5 digits, 7-segment, 14.2 mm (.56")
Red or green LED
-99999 to +99999
-999990 to +999990 (with fixed selectable right-hand zero)
Count by 1, 2, 5, 10, 20, 50, 100
Four LED lamps
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Power
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Voltage, std.
Voltage, opt.
Frequency
Power isolation
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85-264 Vac and 90-370 Vdc
8-28 Vac and 9-37 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
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Excitation Output
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5 Vdc
10 Vdc
24 Vdc
Output isolation
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5 Vdc ±5%, 100 mA max
10 Vdc ±5%, 120 mA max
24 Vdc ±5%, 50 mA max
50 Vdc to meter ground
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Environmental
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Operating Temperature
Storage Temperature
Relative Humidity
Protection
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0°C to 55°C
-40°C to 85°C
95% at 40°C, non-condensing
NEMA-4X (IP-65) when panel mounted
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