Interface description (RS-232) for A&D FX-i and FZ-i precision balances

A&D’s FX-i and FZ-i precision balances are equipped with a serial interface (RS-232) and can be easily connected to a computer for data transfer (if necessary with a converter from RS-232 to USB or to Ethernet). You can, of course, also connect other devices such as a serial printer, a data logger or a secondary display.

I recently tested all communication modes and their various settings in order to update the product description in our German scales shop. Since this took me a lot of time, I also translated my findings into English for publication on this blog.

I found that all commonly used communication modes (a.k.a. transfer modes, transmission modes) are supported and that they can often be fine-tuned in a way rarely possible with other balances. Concerning the data format, the FX-i and FZ-i balances support not only A&D’s standard format, but also several other formats which might make these scales suitable as a drop-in replacement for older Mettler Toledo or Sartorius balances. However, the more recent SICS protocol was not implemented.

The balances support a number of commands for bidirectional communication. Unfortunately, not all applications and settings are accessible via remote commands (for example, the limits for checkweighing cannot be set by a connected computer).

You can use any terminal software to test communication via the RS-232 interface (e.g. HTerm or PuTTY). For productive use, I recommend A&D’s free WinCT software or our Simple Data Logger software. The best integration can often be achieved by customizing your own software to communicate directly with the balance.

RS-232 interface and cable

FX-i and FZ-i balances have a built-in DE9M connector and require a straight (1:1) cable (not a null modem cable):
RS-232 interface on A&D FX-300i balance

Interface parameters

Default settings are highlighted in bold:

Baud rate: 600, 1200, 2400, 4800, 9600, 19200
Data bits: 7 bits or 8 bits
Parity: even, odd (for 7 data bits), none (for 8 data bits)
Stop bits: 1 bit
Data flow control (handshaking): none (RTS and CTS lines are connected internally but not used for actual flow control).

Data format

By default, the balances use the proven A&D format and transmit 17 ASCII characters for each weight value:

First line: number; second line: ASCII characters sent by the balance; third line: hexadecimal value
 1 2 3 4 5 6 7 8 91011121314151617
ST,+00456.89gCRLF
53542C2B30303435362E38392020670D0A

As far as I know, the very first scale from A&D with a data interface already used the same format. This is very impressive, particularly when other manufacturers sometimes change the data format between firmware updates or even between transmission modes.

As alternatives to the A&D format, 5 further data formats can be used. The user manual (PDF) contains a detailed description in chapter 10-6.

Communication modes

The corresponding setting in the menu of the balance is indicated in [square brackets].

  1. Key mode: The weight is transmitted when the PRINT button on the balance is pressed.
    • Mode A: Only when the weight is stable [dout / Prt 0].
    • Mode B: Immediate transmission (stable and unstable weight) [dout / Prt 4].
    • Mode C: The balance waits until the weight has stabilized and then transmits it [dout / Prt 5].
  2. Auto-print: The weight is automatically transmitted after stabilization.
    • Mode A: Return to zero is required before next transmission [dout / Prt 1]. You can set which range around zero counts as “zero” (10, 100 or 1000 digits) [dout / AP-b]. You can also specify whether only positive, negative or all values should be transmitted [dout /AP-P].
    • Mode B: No return to zero is required before the next transmission [dout / Prt 2]. You can set the required difference from the last stable value (10, 100 or 1000 digits) [dout / AP-b]. You can also specify whether lower, higher or all values should be transmitted (compared to the last stable value) [dout /AP-P].
  3. Stream mode: Continuous transmission of 5, 10 or 20 values/s [dout / Prt 3]. The frequency is determined by the display refresh rate [bASFnc / SPd]. This mode is not suitable if you connected a printer or hardware data logger to the balance, but it is required if you want to use an external display. Our data logger software can also easily handle this number of values per second.
  4. Interval mode: Transmission of a value every 2, 5, 10, 30 or 60 seconds or every 2, 5, or 10 minutes [dout / Prt 6].
  5. Command mode: The balance responds to commands received over the interface (bi-directional communication). Available in all modes, see commands below.

In mode 1, 2 and 4, the display blinks to signal that the weight has been transmitted.

Supported commands

“Q” is used to get the weight immediately, while “S” is used to get the next stable weight. All commands must be terminated with carriage return and line feed:

No.: 1 2 3
ASCII:QCRLF
Hex:51OD0A

Complete list of commands (in alphabetical order):

?IDRequests the balance ID (can be set through the menu).
?PTRequests the pre-tare value (which has been set using the PT command).
?SNRequests the balance’s serial number.
?TNRequest the balance’s model name.
CCancels the S or SIR command.
CALSame as pressing the CAL button.
<ESC>PSame as the “S” command. <ESC> is the escape control character (1Bh). Compatible to Sartorius SBI and older Sartorius balances.
<ESC>TSame as pressing the RE-ZERO button.
EXCCalibration using an external weight (only for FZ-i).
QRequests the weight data immediately.
OFFTurns the balance off.
ONTurns the balance on.
PSame as the ON:OFF button (“P” = power?).
PRTSame as pressing the PRINT key.
PTSets a tare value, PT:xxx.x g. The unit must be transmitted using A&D’s format (3 characters, right-justified, padded with spaces).
RSame as pressing the RE-ZERO key.
SRequest the stabilized weight.
SISame as “Q” (compatible to older Mettler-Toledo balances).
SIRSwitch to stream mode (continuous transmission).
SMPSame as pressing the SAMPLE key
TTares the balance.
USame as pressing the MODE key.
ZSame as pressing the RE-ZERO key.

Other settings affecting RS-232 data transmission

You can set the balance to acknowledge valid commands with the ACK control character (06h) and to reply to invalid with “EC” and an error number [SiF / ErCd]. The manual contains detailed information and examples in chapter 16-2.

The terminator can be changed from carriage return and line feed (0Dh 0Ah) to carriage return (0Dh) [SiF / CrLf]. This affects both the output and the input (commands).

It’s also possible to change the decimal point to a comma [bASFnc / Pnt].

The balance can re-zero (tare) itself after sending the weight, which is useful during formulation [dout / Ar-d].

FZ-i balances are equipped with an internal clock and calendar and can output the time, date or time and date [bASFnc / dout / S-td]. According to the manual, this only works when outputting GLP data and not with individual weight values (I will test this later this week). This information can be added to the weight data [dout / S-td].

You can use the animal weighing application to calculate an average weight and automatically output it (as shown in this short video). Statistical calculation mode can output numbered individual weight values and summarized statistical data.

You’ll find further settings in a function table in the user manual (chapter 10).

Further information

 

Raspberry Pi: Connecting a scale can be very easy…

…as long as you choose the right scale! The photo below shows an A&D EK-2000i compact balance connected to a Raspberry Pi 3 Model B using a compatible serial cable and an FTDI RS-232 to USB converter:
Scale connected to Raspberry Pi

Python and pySerial make it easy to read weight data from a scale

On the Pi, I used Python with pySerial to read the weight from the scale. The script I put together is trivially simple. You can download it here or just type it on the Pi:
Script to read weight sent from A&D scale

By pressing the PRINT-Button on the scale, I then sent a few weight values to the Pi and the script wrote them to the terminal (b’ is added by Python):
Weight printed to terminal

In a more useful application, you would want to parse the data sent from the scale to get the weight as a number and then do something with it (maybe write it to a database). You could also do interesting things with the GPIO on the Pi like sounding an alarm when a certain weight is exceeded (though a microcontroller might be better suited for this).

I then switched the scale to “stream mode” (continuous transmission) where it sent 10 values per second (stable or not). The output you see below is the result of placing a single object on the scale and waiting for it to stabilize:
Weight data in continuous mode

I hope this example shows that it can be really easy to transfer the weight from a scale to a Raspberry Pi.

Notes on scales and the Raspberry Pi

One advantage of A&D scales is that (almost) all of them use the same data format and interface parameters and that you’ll find a good description in the manual:
A&D EK-i balance data format

However, you could use also use scales made by other manufacturers as long as they come with an RS-232 interface and the ability to send the weight in ASCII format. Available data output modes vary, so please read the product description carefully before buying.

A converter like the one I used is already built into some scales, which means that you can directly connect them to the Raspberry Pi via USB (you won’t need a serial cable). You’ll find many Ohaus scales with this interface option and the ones I’ve tested worked fine. However, cheaper scales with a USB interface can often not be used with pySerial as they do not emulate a serial port. They can also present other challenges (e.g. data that is not transmitted in human-readable ASCII format).

You do of course not have to use Python, just make sure that your preferred programming language can communicate over a serial port on the Pi. The book Raspberry Pi with Java: Programming the Internet of Things (IoT) contains projects using Ohaus scales and, well, Java.

Finally, please don’t try to use the serial interface already provided by the Pi on the GPIO pins without a logic level converter (RS-232 voltage could reach up to 15V). Excellent further information on serial ports on the Raspberry Pi can be found here.

How to connect your scale to a network (Ethernet) using Moxa’s NPort 5110A

Many scales and balances are equipped with an RS-232 interface. Moxa’s NPort series and similar serial device servers allow you to connect such scales to a network (Ethernet). In this article, I’ll show you how to connect a Moxa NPort 5110A to an Ohaus scale and how to configure and test it.

1. Physical connection

The Moxa Nport 5110A has an RS-232 port (DE9M) on one side and an Ethernet port on the other side:

Data cables (red) are not included.

To communicate with your scale, you’ll need a matching RS-232 cable. The Ohaus Defender 3000 scale used in this example requires a DE9M to DE9F straight (1:1) cable:

Ohaus scale with Ethernet connection through Moxa NPort 5110A

Once the physical connection to the scale has been established, the Moxa NPort has to be configured. There are several ways to do so. I prefer the following method:

  1. Connect the NPort directly to a single computer (not a LAN) with an Ethernet cable.
  2. Use the NPort Administator software included with the device to configure it.

2. Network configuration

Start the NPort Administrator and locate your NPort by clicking on the Search button:NPort Administrator: Search

It should be found at the default IP address (192.168.127.254).

Note: It’s not always necessary to change your PC’s IP address if you’re running the NPort Administrator software. However, if you receive error messages during the following steps, try to temporarily set your computer’s IP address to an address on the same subnet (such as 192.168.127.1).

Select the Ethernet connection under Control Panel > Network and Internet > Network connections, right-click on it and choose Properties, then select Internet Protocol Version 4 (TCP/IPv4) and click on Properties. Make a note of your current settings so that you can restore them later, then enter the temporary IP address:
Ethernet IP address setting in Windows 10

If the NPort is shown as locked, right-click on it and select Unlock:
NPort Administrator: UnlockThe default password is “moxa”.

Right-click again and select Configure, then select the Network tab:
NPort Administrator: Network configurationEnter a static IP address, subnet mask and gateway that work on your network (or select DHCP or BOOTP for automatic address assignment, though this is not recommended for most operating modes).

To make the NPort accessible on our network, I set its IP address to 192.168.0.253:
NPort Administrator: Modified network settings

With the network configuration complete, you can disconnect the NPort 5110A from your computer and connect it to your network (LAN).

3. RS-232 configuration

It is essential that both the NPort and the scale use the same settings for the serial port (RS-232). In the Serial tab, select the port (the NPort 5110A only has one, but you still have to select it), check Modify and click on Settings:
NPort Administrator: Default serial settings

Enter the RS-232 settings found in your scale’s menu or user manual. The default settings of our Ohaus Defender 3000 scale are shown in the screenshot below:NPort Administrator: Serial configuration (RS-232)

Important: By default, the NPort is set to CTS/RTS flow control! You cannot change this setting when using the Setup Wizard through the web console. As mentioned before, I recommend using the NPort Administrator software instead.

4. Set an operating mode

To change the mode, go to the Operating Mode tab, check Modify, select the port and click on Settings:NPort Administrator: Operating Mode

The NPort 5110A supports several operating modes, I will only discuss the following two here:

  • Real COM mode: This mode allows you to create a virtual COM port on a PC and use the scale as if it were connected directly to that PC. This is very useful when you’re using software which only supports connections to COM ports and cannot communicate over TCP/IP (such as our 232key virtual keyboard wedge software).
    Please note that you’ll have to install a virtual COM port driver on the PC that communicates with the scale. In my tests on Windows 10, setting up the COM port through NPort Administrator did not create a new virtual COM port on the system. However, using the NPort Windows Driver Manager worked.
  • TCP Server: The NPort acts as a server, waiting for incoming connections from TCP clients on port 4001 (or on another user-defined port). The maximum number of concurrent connections can be changed from 1 (default) to up to 8. This mode works with software like our Simple Data Logger and many others.
    NPort Administartor: TCP Server mode

    Note: It is not necessary to set the data packing options unless you want to optimize either for minimal latency or maximum throughput. By default, the device will try to find a reasonable compromise (this is likely achieved by observing the delay between the data received over RS-232 to determine when a “line” of data is complete).

    When I set the scale to continuous transmission mode (wich has no delay between the weight values), the NPort packed 104 bytes in each Ethernet frame, corresponding to almost 6 weight values (the scale sends 80 values/s):
    Wireshark screenshot

For further details and for information on the other modes, please consult the user manual.

5. Run a test

Depending on the operating mode chosen above, you’ll have to use different programs to test the NPort 5110A. In addition to the software I’ve already mentioned above, you could use the following:

Real COM mode

A terminal program like Termite or HTerm can connect to the virtual COM port. Make sure that the connection parameters correspond to the settings of your scale.

TCP Server

You can use PuTTY set to “Raw” TCP mode to act as a TCP client:
PuTTY configurationThe following screenshot shows commands sent to the scale and the replies:PuTTY communication with Ohaus scaleAnother option is our free TCPTester software. It repeatedly sends a user-defined command to the scale (e.g. to request the weight). Once a reply has been received, the command is repeated:

TCPTester tcp utility used to test Moxa NPort connected to Ohaus scale
TCPTester free TCP test utility available from Smartlux

During testing, it can be useful to observe the LEDs on the NPort:

  • The “Ready” LED should be green.
  • The “Link” LED is green when the NPort has established a 100 Mbs Ethernet connection and orange on a 10 Mbps connection.
  • The Tx/Rx LED flashes orange when the NPort receives data from the scale and flashes green when the NPort is sends data to the scale over the serial port. Therefore, If you’re sending commands to a scale, you should be able to see it flash green. A reply from the scale would cause the LED to flash orange. If this is too difficult to see, consider using the web console to diagnose connection issues (I found it worked best in Firefox):
    Moxa web console monitor async

I hope this article has been useful. What are your experiences with Moxa’s NPort serial device servers? Please don’t hesitate to leave a comment! For support, please contact Moxa or your vendor.

Purchase a PDF version of this article (contains no additional information). 

Record the weight from a scale or balance to a file – Simple Data Logger software

Connecting your scale to a PC and recording the weight should not be a difficult task. However, data logging software available from scale manufacturers or third parties is often expensive, difficult to use or frustratingly unreliable. We developed Simple Data Logger (SDL) to address these issues.

SDL writes the weight received from a scale or balance to a file, optionally adding the date and time. The CSV files generated by SDL can easily be opened in Excel and other spreadsheet applications for further processing and visualization.

Recording the weight from a precision balance using Simple Data Logger

SDL currently supports the following connections:

  • COM port: RS-232, USB virtual COM port, Bluetooth SPP, etc.
  • TCP/IP: Ethernet, WLAN (raw TCP format only).

Note: Your scale has to send data in ASCII format.

Get started recording weight values with Simple Data Logger

Connect your scale to your computer, download and install SDL, then follow these steps to configure the software (updated on December 7, 2019 – please refer to the documentation on the SDL website for the latest instructions):

  1. Input tab:
    Input tab: A&D scales and balancesIf your scale or balance is listed in SDL, simply select it and press the set default parameters for device button. Otherwise, select “generic measuring instrument” and enter the interface parameters manually. Set the radio button to match your connection: COM port (RS232, USB VCP, Bluetooth SPP) or TCP/IP.Make sure that you’ve specified a terminator (a.k.a. delimiter, the last character your scale sends in each line of data) or a timeout (e.g. 100ms, SDL will process received data if no additional data is received during this time).
  2. Output tab:
    Output tab (English US)Choose a file for the recorded data. SDL will create if for you if it does not exist (otherwise, data will be appended). Choose (or enter) a date and time format or select “None” from the list if you do not want SDL to add the date or time. Pick a decimal separator (for numeric values) and value separator (used to separate values from each other). The correct settings for your locale can be made automatically by clicking on the set values button.
  3. Start tab:
    Start tab: A&D FX-300i balancePress the start button to start recording data. Press the “PRINT” button on your scale or balance to send the weight to SDL. Depending on you scale, this button might have a different name (e.g. “DATA”). Some scales like the A&D FX-300i used in this example also have to ability to automatically transfer each (stable) weight. Data received will be shown in the event log (with the captured weight value shown in blue) and the weight will be written to the chosen file. Press stop to stop data logging and to close the file.

    Note: SDL can also handle continuous streams of weight data if this is what your application calls for (we’ve tested it with a scale which sends 100 values per second). The total number of recorded values is only limited by your disk space (but please keep in mind that Excel cannot open files containing more than 1,048,576 rows).

Process the weight values in Excel (or other spreadsheet applications)

Provided that you’ve made the right format settings in the output tab, you can easily open the CSV file in Excel (or other spreadsheet applications like Google Docs, OpenOffice/LibreOffice Calc). The weight will be recognized as a number, allowing you to make further calculations (i.e. calculating the total weight as shown below):
Everything shown here can be done with the “Basic” version of SDL (which is free for personal, non-commercial use). The “Plus” version has additional features including a timer to request the weight from the scale in user-defined intervals.

Very affordable licences can be purchased from our partner FastSpring (immediate license delivery).

 

Links and further information

Free software for scales and balances with RS-232 and USB

Are you still manually entering weight readings from your scale or balance on your PC? Is your scale equipped with a RS-232 or USB (virtual COM port) interface? If yes, you can eliminate manual data entry by connecting your scale to your computer and using our free software 232key.

232key automatically types the weight into any application

Our software runs in the background, listens to the COM port (serial port) your scale is connected to and waits for measurement values sent by the scale. Those values are then filtered, formatted and typed into the application running in the foreground at the current cursor position as simulated keystrokes. This means that 232key can be used to transfer the weight (or other measurement values) into any application that accepts keyboard inputs, e.g. Microsoft Excel, OpenOffice / LibreOffice Calc, Google Docs, a form on a website, etc.

In the following example, I used A&D’s FG-60KBM scale with an optional RS-232 interface (FG-OP-23). I connected it to my laptop with A&D’s serial cable (AX-PC09-SCA) and an inexpensive converter to USB (as my laptop doesn’t have a serial port). Upon pressing the “PRINT” key on the scale, the weight was typed directly into an input field on a website:
Transferring the weight from a scale to a website

Compatibility with scales and balances

To use 232key, you’ll need a scale with a RS-232 interface (aka. serial port, COM port, EIA-232) or an interface which appears as a (virtual) COM port when the scale is connected to your PC. This is the case for many (but not all) scales with a USB interface and for scales which support the Bluetooth Serial Port Profile.

Your scale or balance also has to send the weight in ASCII format. The weight has to be the first numeric value sent* and it should only be sent once (after you’ve pressed a key on the scale), not continuously.

The vast majority of scales and balances available on the market today fulfills these requirements. Just to give you a few examples, you should be able to use 232key with most or all scales and balances made by A&D (RS-232 only), Adam Equipment (RS-232 and USB), Ohaus** (RS-232 and USB), Kern**, MyWeigh (RS-232 only) and other well-known brands. New device profiles are constantly added!

Finally, an easy way to transfer data from your scale to your PC

We designed 232key to make your life easier. No complicated configuration is required. If your scale manufacturer or model is included in the list of predefined devices, you don’t even have to manually enter the interface parameters: Simply select your scale and click on “Default” to load the settings.
Interface settings

Not sure which COM port you scale is connected to? Press the “Auto” button and 232key will try to detect the port automatically (works with all devices which have some sort of hardware handshaking functionality, e.g. scales and balances made by A&D and MyWeigh’s popular HD series).

Do you know which decimal separator (point or comma) your scale is using? Why should you! 232key understands both input formats and lets you choose which output format you want.
Decimal separator

Would you like 232key to press an additional key after typing the weight, e.g. the “Enter” key to jump to the next row in a spreadsheet? No problem, simply specify the desired key in the “Format” tab.
Additional key

All of these useful and user-friendly features are available for free! Additional functionality is available in the paid “Plus” version of 232key.

Download and documentation

Please visit our product website 232key for further information and to download our free software. Should you have any questions or suggestions, please don’t hesitate to post them in our support section or as a comment below.


* We’ve added an exception to this rule for scales and balances made by Adam Equipment.
** Affiliate links.

Update May 2018: Write the weight to a file

232key is a great solution for sending the weight from your scale to an application running on your PC (as simulated keystrokes). In some cases, however, it makes more sense to record the weight to a file which is later opened in Excel (or other applications).

This is particularly true for unattended data logging applications running over long periods of time. Another example are applications with high data rates (several weight values per second) which would overwhelm a virtual keyboard wedge like 232key.

For these use cases, we’ve recently released Simple Data Logger, an easy to use solution for recording the weight sent from your scale to a CSV file. You can read more about it on this blog or on www.smartlux.com/sdl.