Introduction: How to Connect an Electronic Balance or Scale to a PC and Read Weight Values Directly Into Excel

Most electronic scales and laboratory balances have an RS232 (Serial) or a USB port however no instructions are normally provided to show you how to correctly connect it to your PC or how to input weight values directly into programs like Excel or Access. The steps below will show you how to connect your scale to a PC and identify what port the scale is connected to and also how to input weight readings directly into Microsoft Excel.

The only things that you will need are an appropriate cable that connects from the scale to your PC and a Windows program called a "Software Wedge". In this example, we will use a product called BC-Wedge from TAL Technologies, Inc..

Note: This tutorial assumes that your scale or balance has a "Print" button that will transmit weight values to a PC. Most scales and balances do have one although it may not be marked clearly. You may need to read the users manual for the scale or contact its manufacturer to learn exactly how it works. If your scale does not have a Print button, it does not necessarily mean that you cannot send weight data to a PC. It means that you probably need a more advanced software wedge like the WinWedge product from TAL Technologies.

Step 1: Identifying USB Cable Connectors

If your scale has a USB connection then you would need to determine what connector is on the scale. The USB ports on a PC are always Type A USB ports therefore if your scale has a Type B USB port, you would need to get a USB cable that has a Type A connector on one end and a Type B connector on the other. Shown above are the most common USB ports found on most scales and balances along with pictures of the connectors that fit the ports.

Important Note: If your scale has a USB connector then it should come with a device driver that you will need to install in Windows in order for the scale to show up as a standard COM port in Windows. Sometimes this device driver is supplied on a CD that comes with the scale and sometime you need to download the driver from the manufacturer's web site. If your scale has a USB connection but does not come with a driver or if you fail to install the driver, then it will not be possible to read in data from the scale using off-the-shelf software tools (like the BC-Wedge software wedge) and you will need to contact the scale's manufacturer to find out what software tools they have that you can use.

Step 2: Identifying RS232 Cable Connectors

If your scale has a RS232 port, it will usually be located on the back of the scale and it should look like one of the ports shown above. It is more common for a scale to have either a 9-Pin male connector or a 25-Pin female connector. Serial ports found on the back of a PC will always be either 9-Pin Male or 25-Pin female. Almost all PCs built in the past 10 years that have serial ports will have 9-Pin male ports and usually only very old PCs will have 25-Pin serial ports. If you need to connect a 9-Pin cable to a 25-Pin port or if you need to connect a 25-Pin cable to a 9-Pin port, you can purchase 9 to 25 pin adapters at most computer or office supply stores or on for under $10.00. Just make sure that you match male and female connections correctly.

RS232 cables come in two varieties called "Modem Cables" and "Null Modem Cables". Modem cables have the wires in the cable running straight through and Null Modem cables have the transmit and receive lines crossed in the cable. Most scales will typically connect to a PC using a Null Modem cable however there are exceptions. One way to make sure that you have all your options covered is to purchase a "Null Modem Adapter". A Null Modem Adapter is a small connector that slips in line with the cable and crosses the transmit and receive lines. A Null Modem Adapter will convert a Null Modem Cable to a Modem Cable and a Modem Cable to a Null Modem cable. They are also available on or at any office supply store for under $10.00.

Once you know the types of connectors that are on both your scale and your PC, you would connect the two together using an appropriate cable. If your scale comes with a cable, then that would be the best one to use. If not, you can purchase cables in any configuration or length that you want., or any office supply store should have what you need. You may want to contact the manufacturer of the scale to find out if it uses a Modem or a Null Modem cable before making a purchase.

Note: The Parallel ports on a PC are also 25-Pin ports however they are always 25-Pin male connectors. Parallel ports on a PC are generally only used for connecting to a printer. They are not serial ports and cannot be used to communicate with a scale.

Step 3: RS232 to USB Converter Cables

If your scale has a RS232 port but your PC only has USB ports, you can purchase a RS232 to USB converter cable at any computer or office supply store for under $25.00. The best ones use either FTDI or Prolific chipsets. also sells them for around $10.

All RS232 to USB converter cables require a driver to be installed in Windows in order for the cable to work. Typically the driver is provided on a CD with the cable and you normally install the driver first before you connect the cable to your PC for the first time.

Step 4: Determining the COM Port Number

On most PCs that have a single built in COM port, the port will appear to Windows as COM1 however this is not always the case. If your scale uses a USB connection or if you are using a RS232 to USB converter, you will need to determine the COM port number that the device is connected to. The best way to do this is to look in the Windows Device Manager in the section labeled "Ports (COM & LPT)". This section will contain a list of all COM ports that are installed on your PC.

Note: If your scale connects directly to a USB port or if you are using a RS232 to USB converter, make sure that the scale or the converter is connected to the PC and that it's device driver is installed before looking in the Device Manager.

Step 5: Download and Run the BC-Wedge Software

Once you know the COM port that the scale is connected to, you can download the BC-Wedge software Setup program from the web site using the following URL:
The file is a ZIP file so you will need to save it to a folder on your PC and then extract its contents using the Windows File Explorer and then run the Setup.exe program that was extracted from the ZIP file. After you install BC-Wedge, run it and select the COM port for your scale from the COM Port drop down list in the main BC-Wedge window.

The BC-Wedge software was primarily designed to input data from a bar code scanner however it can also be used with most scales and balances. TALtech has a full line of Software Wedge products that have much more advanced features than what are available in the BC-Wedge program. You can learn more at:
For the purpose of this tutorial, BC-Wedge should work just fine.

Step 6: Running the BC-Wedge Software and Selecting the Communications Settings

Now that you have your scale connected to your PC, the next step is to determine the serial communications parameters that the scale uses. The very best way to do this is to either look in the scale's user's manual or contact it's manufacturer. You will need to know the Baud Rate, the Parity setting, the number of Data Bits, and the number of Stop Bits. In order for your PC to communicate with your scale, the settings that you select in the BC-Wedge software must exactly match the settings that your scale uses. (The "Flow Control" option and the "Scanner Beep String" can be ignored.)

To enter the serial communications settings in BC-Wedge, you would click on the "Settings" option in the BC-Wedge main menu. This will display the window shown above where you would enter the communications settings. 

Note: You do not have to change any serial communications parameters in the Windows Device Manager. The parameters that you select in the BC-Wedge software (or any other software) will always override any parameters set in the Device Manager.

Step 7: Testing the Connection to the Scale

If you have the correct communications parameters set in the BC-Wedge software, you should be able to see a weight reading in the text box labeled "Input Data From Scanner" when you press the Print button on your scale. The image above shows typical data from a scale. If no data appears after you press the print button then you may have the wrong COM port selected. If data appears but is garbled or completely unreadable then you have the right COM port but the wrong serial communications parameters selected. You may need to experiment with different settings until you see data that looks correct. Try setting the Number Of Data Bits to "7", and the Parity to "Even" and then try each different Baud Rate until you see data that contains weight values that match what is on the scale's display.

Step 8: Inputting Weight Values to Cells in Excel

Once you are able to see data appear correctly in BC-Wedge, leave it running in the background and launch Microsoft Excel and put the cursor in a cell where you want your weight values to go and press the Print button on the scale. If everything is working correctly, you should see the weight value appear in Excel. BC-Wedge works by tricking your PC into behaving as if the data coming in the COM port is coming in from a keyboard. Because of this, you should be able to send weight values directly into any program that you can type data into - including database programs, shipping software, or just about any other Windows program.

Note: If you want just the weight values (without leading spaces or the units) to be stacked in a column in Excel automatically each time you press the Print button, check the checkbox labeled "Filter Out Non Numeric Characters" and select the word "{DOWN}" from the "Postamble Keystrokes" dropdown list in the BC-Wedge window. You can learn about other features available in the BC-Wedge program by selecting Help - Index from the BC-Wedge main menu.