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Scale Meter Frequently Asked Technical Questions
The load cell meter described in https://www.laurels.com/loadcell.php and the scale meter described in https://www.laurels.com/scalemeter.php are similar meters and typically both typically use the same load cell signal conditioner board. Capabilities built into the scale meter’s firmware provide specific features applicable for weighing applications. In most cases, the slightly less expensive load cell meter will also work great for weighing applications. It can be interfaced to the same types of load cells, and it can be scaled to display in units of weight such as pounds, tons or kilograms.
Relay setpoint offset to stop fill operations before a final weight is reached. Count-by function so that the display is rounded off to multiples of 1, 2, 5, 10, 20, 50 or 100. Selectable fixed right-hand dummy zero for a six-digit display to 999990. Auto-zero function to compensate for load cell drift. Auto-tare in additional to manual tare. Please see the explanatory paragraphs in https://www.laurels.com/scalemeter.php.
Yes. A summing box is simply a clean way to connect the meter to the 6 wires of multiple load cells in parallel. Up to four linear load cells of the same type can be connected in parallel and be powered by the same 10 Vdc, 120 mA excitation output of a Laureate scale meter. For example, four load cells can be used to support the four corners of a weighing platform. Each 350 ohm load cell will draw an I=V/R current of 28.6 mA, so that the total current requirement for four load cells is 114.4 mA. For scaling purposes, multiply the weight read by each load cell by the number of load cells, since each only carries part of the load. The best way to scale a system with multiple load cells is to use the "Reading Coordinates of 2 Points" scaling method, which uses actual weights.
Most scale meters use a load cell as the sensor, which provides a 0-20 mV or 0-30 mV output. Meter scaling is the process of converting the load cell output in millivolts to a reading in units of weight. For example, meter scaling would be the setting which allows the scale meter to convert the 0-20.000 mV DC output of a load cell to a 0-5000 pound weight reading.
Simply enter data from the load cell label. For example, the label may state 10V excitation, a load rating of 5000 lbs, and 2.020 mV per volt sensitivity. This means 0 mV should be displayed as 0 lbs, and 20.20 mV should be displayed as 5000. To enter this data into the meter, go to the front panel menu item “SEtuP” and select “Coordinates of 2 points method.” Enter Lo In as 0.000 mV, Hi In as 20.200 mV, Lo Read as 0 lbs, and Hi Read as 5000 lbs. The scale meter will interpolate between these two points to convert the received millivolts to a weight reading in lbs.
The meter’s “Reading coordinates of 2 points method” is most accurate since it scales the meter and load cell as a system by using known reference weights. First zero the scale by not applying any weight and enter zero as the desired reading. Then apply the reference weight and enter its known weight as the reading. Go to the meter’s front panel menu item “SEtuP” and select “Reading coordinates of 2 points method.” The meter will prompt you to measure Lo In and High In, and to enter values for Lo Read and High Read. The scale meter will interpolate between these two points to convert the received millivolts to a weight reading in lbs.
The ordering process for Laureate meters with a WM1 load cell signal conditioner board requires that min input, min reading and max input, max reading be specified at the time of order. This information allows Laurel to set the meter range, which can be ±20.000 mV, ±50.000 mV, ±100.00 mV, ±250.00 mV, or ±500.00 mV. This initial setup can easily be changed by the user by moving jumpers and changing scaling via the meter’s front panel, as explained in the Scale Meter Owner’s Manual.
Laureate meters are modular with slots for a choice of power supply boards, signal conditioner boards, analog output boards, relay boards and communication boards, as illustrated in our Laureates Overview web page. These boards can be ordered installed with a new meter, but they can also be purchased separately later and be simply plugged in. The presence of a new board and the type of board are automatically sensed by the meter’s firmware or by  Instrument Setup (IS) software. If you change boards, also change the model number on the meter label.
The Laureate scale meter offers special software feature for weighing and can use either a load cell signal conditioner board (WM1 in the model number) or a process signal conditioner board (P1 or SG1 in the model number). The load cell board is recommended for weighing applications, since it offers a resolution down to 1 microvolt per count, while the process board is limited to 10 microvolts per count. The load cell board can also be set up for a 6-wire connection, while the process board is limited to 4 wires. Both signal conditioner boards can be used with the same types of load cells and can be used to scale millivolt signals for display in units of weight such as lbs or kg.
Annual calibration to NIST standards can be performed by Laurel and by some of its distributors as a service. It can also be performed by the customer using Laurel’s free Windows based  Instrument Setup (IS) software. Open the Main Menu of IS software, click on Calibration in the top menu bar, and follow the prompts. An external DC voltage standard is required. Also required in the meter is a communications board, like the Laureate P/N LUSB USB interface board. Following calibration, that board can be removed and be used in another meter.
Analog output scaling is the process of converting the meter reading to an analog output, which can be user selected as 4-20 mA, 0-20 mA, 0-10V or -10 to +10V. Simply enter the load cell meter readings for the bottom and tops of the selected analog output range, and the output will be interpolated linearly between these two readings. Please see  Section 17 of the Laureate DPM user manual.
Chances are that your meter is set for the factory default analog output, which is 4-20 mA, and is applying 12V to force a current into an open circuit. To set your meter to a 0-10V or -10 to +10V analog output, set jumpers for unipolar 0-10V or bipolar -10 to +10V operation, select the desired range and scaling, and connect to the correct analog output pins, as explained in the Scale Meter Owner’s Manual.
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