Digital Scales Blog by Smartlux

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

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

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 parsed, 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. Ideally, the weight should be the first numeric value sent and it should only be sent once (after you’ve pressed a key on the scale or on stability), not continuously.

The vast majority of scales and balances available on the market today fulfill these requirements. To give you a few examples, you should be able to use 232key with most or all scales and balances made by A&D, Mettler-Toledo, Ohaus, Sartorius 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 Set defaults to load the settings.

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

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.

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 Output tab.

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. There you’ll also find the documentation, an extensive troubleshooting guide and FAQ. Should you still have questions or feature suggestions, please post them in our support forum or as a comment below.

Do you prefer to write the weight to a file instead?

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 opened later (e.g. in Excel).

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 your PC when sent as keyboard inputs.

For these use cases, we’ve created 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.

Article last changed on November 19, 2020: Screenshots and some links updated.

Easily weigh aquatic animals using submersible scales

Regularly recording an animal’s weight is essential for keeping track of its health. However, weighing can be a traumatic experience particularly for aquatic and semi-aquatic animals as they have to be removed from the water where they spend all or most of their life.

Fortunately, several weighing instrument manufacturers have addressed this issue with new submersible scales. One such scale is the Ohaus Valor 2000W, shown below being partially submerged to facilitate the weighing of one of our company’s turtles:

Weighing a turtle on a semi-submerged scale — Turtle “Alpha” basking on top of the scale.

Thanks to it’s unique “flow-thru design which channels fluids that may enter the housing through strategically located drain holes”, this scale immediately sinks to the bottom of the aquarium while remaining fully operational. All that’s left to do is to wait until the animal takes a rest on the weighing pan and record the weight. There’s no better way to weigh aquatic reptiles, fish and marine mammals!

Available in capacities from 1.5kg to 15kg, Ohaus’ Valor 2000 can be found here.

How accurate are smart scales?

Are smart scales accurate weighing instruments or just simple bathroom scales with expensive connectivity features? To find out, I tested the Withings WS-30, Fitbit Aria and A&D UC-324NFC using class M1 weights.

A&D UC-324NFC Fitbit Aria Withings WS-30 — This image by digitalscalesblog.com is licensed under a Creative Commons Attribution 4.0 International License

Preparation

Each of the scales had not been used before and was configured as instructed by the manufacturer. This included signing up for an account with Withings and Fitbit. In the case of A&D’s UC-324NFC, I took advantage of a function available in the Wellness Connected app which let me “calibrate” the scale by entering the local gravitational acceleration.

The scales were tested under similar conditions with a stable temperature of around 22°C and were placed on a flat, hard surface. The Withings and Fitbit scales were left alone for a night after the initial configuration as I wasn’t quite sure how they determine the zero value: unlike older electronic scales, you don’t have to switch them on and wait for them to show ‘zero’, instead, you step right on (the UC-324NFC determines the zero point after you step off).

Test procedure

I used 20kg weights to test the scales at 40, 60, 80, 100 and 120 kg. This procedure was repeated 3 times for each scale (I did a lot of weight lifting that day).

Results

The first column gives you the nominal weight (in kg) and the next three are the values as shown by the scales.

Withings WS-30

40	40.2	40.2	40.2
60	60.3	60.3	60.3
80	80.4	80.3	80.3
100	100.3	100.4	100.4
120	120.4	120.4	120.4

Fitbit Aria

40	40.2	40.2	40.1
60	60.2	60.2	60.2
80	80.2	80.2	80.2
100	100.3	100.3	100.3
120	120.3	120.3	120.4

A&D UC-324NFC

40	39.95	39.95	39.95
60	60.00	59.95	60.00
80	80.00	80.00	79.95
100	100.00	100.00	100.00
120	120.00	120.00	120.00

As you can see, A&D’s UC-324NFC was the most accurate scale, never deviating by more than 50g from the true value. Its 50g resolution and gravity compensation function certainly paid off.

However, the Fibit and Withings scales did a great job, too. Looking at the measurement results in each row, you’ll see that they are either identical or off by just one scale interval (100g). We can therefore say that these scales were slightly less accurate, but still very precise* (or that their repeatability was still excellent). As far as your body weight is concerned, you’ll generally be less interested in absolute values and more in tracking changes (“am I loosing or gaining weight”) and these scales would be perfectly suitable for this purpose. Nevertheless, I was a bit surprised that Fitbit and Withings didn’t use the location I had entered during account creation to adjust the scale for the local gravity acceleration. This would most likely have improved their accuracy.

Overall, the results are very good. As far as I can tell from this test, you’re not just paying for the “smart” features, you get accurate scales, too.

Further information / where to buy:

Withings website – amazon.com – bestbuy.com – newegg.com – amazon.co.uk – amazon.de
Fitbit website – amazon-com – bestbuy.com – amazon.co.uk – amazon.de
A&D Wellness Connected UK website – amazon.co.uk – amazon.de

Disclosure:

Some links above are affiliate links.
My company used to sell A&D’s UC-324NFC in our German scales shop, but we don’t anymore. The Withings WS-30 and Fitbit Aria were purchased at retail prices, A&D’s UC-324NFC was purchased with a dealer discount.

*Meaning of accuracy and precision (as used in this article):

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