Using the Load Cell

Use this set of instructions when working with the load cell and PanelX software.

Download the software from the HBM web page. You will also need to download the driver for the RS485 to USB adapter from NI.

Connecting the load cell to PanelX

Connect the USB cable to a Windows computer.
Turn on the power supply (the black box) and wait a few seconds.
Start the PanelX program; a "Device scan" window will open automatically.
Check the box next to RS232/RS485.
Make sure the Baud rate is set to 38400.
Click Scan.
When the scan has finished, the number and the sensor information will appear.
If the number of devices is zero, then you must perform the scan again or check if there are any problems with the connections of the load cell.
Close the window by clicking OK.
Your display should now look something like this.

Begin Working with PanelX

Go to the top menu and click on Options.
On the Options menu go to User level.
Select the Administrator user level so that all the menu items are available.

Application:

Go to the Application tab.
Select Checkweigher. This is used in industrial applications and I didn’t notice any change in the measurements when using standard or checkweigher. Use the one you like.

Adjustments:

Before working with the load cell, certain adjustments are necessary.

Click on the Adjustment menu icon:
Select the decimal point configuration to: *******. This setting will display a number in this form: XX.

To make it have one decimal point, click on the x10 icon.

A number in this form should appear on the measurement window: XX.X
Choose the measuring unit. (i.e. “g” ).
In this decimal configuration, the highest resolution is of 1g. Therefore, select 1 g in the Resolution drop down menu.
Set the nominal value to 20000 g. This is supposed to be the range of the measurements you are performing; however, the load cell only displays correct data when the nominal value is set to 20000 g.

Your configuration should look like this:
Click on Write.

Filters

Filters are used to cut off certain frequencies and prevent the program from displaying noise.
The filters used for dynamic weighing are the 1: FIR32, 3: IIR4 (fast track), 4: FIR64, and 5: FIR64 filters.

Go to the Filter tab.
Select the filter that most suits you.
Recommended settings:
Click on Write.

More on filters:
The 3rd filter : IIR4 (fast track) provided stable values with little noise - almost constant lines with a 0.1 g variation. Be careful when setting the cutoff frequency because if you choose a small cutoff frequency, you lower the sensitivity of the load cell. You will obtain a slow reaction time if cutoff frequency is 0.1 Hz. Try using 1.5 Hz; this will give faster reaction times. If you don’t observe changes in your experiments, then try elevating the cutoff frequency so that the load cell becomes more sensitive to change.
You might want to play with filters and their cutoff frequencies to see which one is most suitable to your experiment; just remember which filters are the ones recommended for dynamic weighing and the effect of elevating or reducing cutoff frequencies.

Taking Measurements

The scope tab lets you see the measurements that you are taking and graphs them through time. We will set the scope measurement to the Standard analysis.

Click on the Scope tab.
On the Mode drop down menu, select the Standard option. This will plot the values measured vs. time.
From the Time window menu, select how much time you want displayed on the chart (i.e. 1 min time window). This does not mean that the program collects data for a minute and then stops. For example, selecting a 1 minute time window will make the chart display only the last minute's worth of data, but the program collects all data between the time you hit the Start and Stop buttons.
On the right side of the scope window, go to the Chart tab and click on Auto vertical zoom. In this configuration, the zoom adjusts to the values you are measuring.
If desired, you can also set a range and a fixed zoom.
Before you start measuring, make sure the measurement display is showing a correct value. In order to set the measurement display to zero, click on the Tare button.
Once you have set up everything and are ready to measure, click the Start button to start measurements.
When you are finished taking measurements, click on the Stop button to stop recording data.

Observations

Notice how the time window shifts to the right as the time you had specified in the time window is surpassed. If you want to copy the chart picture, click on Copy Chart. This will take a picture of the chart that is displayed at that moment and allows you to paste it into a document.

More on the Scope Window

In the scope area, once the time interval has been reached, the program performs some statistical operations on the data displayed on the graph. Note that these statistical properties are calculated from the data currently displayed on the graph, not the entire set of data. To change what data is displayed on the chart, you can click and drag on the time axis.

The quick analysis is displayed like this:

Legend:
Symbol Meaning
Max Maximum value on display
Min Minimum value on display
Δ Max-Min
ϕ Mean
σ Standard deviation
Δt Time interval

The Cursor tool

The Cursor tool (located under the Chart tab) allows you to perform data analysis on a specified interval of data.
Click on the cursor tool to enable it and select the interval you want to analyze.
Information of that time interval will appear on the screen.

Observations of the scope measurement graph:

In the measurement display, you see a number in the form of XX.X if you clicked on the x10 button. So, in the scope data, even though the measurement display shows a value with a decimal point, the graph eliminates this decimal point and will show a number in this format: XXX.
For example, if your measurement is 57.1, the scope data will display a value of: 571 g, so the recommended thing is to try a known measured quantity and familiarize yourself with how the scope window shows the data measured.

Saving the scope data:

On the File drop down menu in the top left corner of the window, click on Save scope data. This will create a CSV file with time and measurement.

Restoring to Factory Settings

If you need to restore the load cell to factory settings, you must close PanelX and then open the AED Panel_32 program on the computer. A description of how to open this software is here.

Once the load cell appears in the AED panel, follow these steps.

In order to reset to factory settings, we must issue a command via the command line of the program.
Go to the Commander tab.
Type the following command and press enter: TDD0.
Once this is done, you must again perform the configuration as described in the previous sections of this wiki page. Perform a series of measurements with known quantities to make sure the load cell is working properly.

University of Texas Fire Research Group