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How to Set Up a Direct Connection Between Sunmi POS and Your Scale

Connect a supported scale directly to your Sunmi POS, with no scale adapter, so weights flow straight into Cents.

Written by Euri

Connecting your scale directly to the Sunmi POS removes the scale adapter from your setup. The scale draws power from the Sunmi and sends weights straight into Cents, and it works across every supported scale brand.

What you'll need

  • A supported scale: Mettler Toledo, Avery, or CAS (including BW and PW models, and CAS PB).

  • A USB-to-serial (RS-232) cable with an FTDI chipset, which works across all supported scales. One cable confirmed to work is the OIKWAN USB-to-RS232 DB9 (FTDI, 10 ft).

Disconnect the scale adapter (If you have one)

  1. Turn the scale over so you're looking at the bottom.

  2. Remove the scale adapter cable from the scale (indicated by the red arrow).
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  3. Unplug the power cord from the scale adapter so it's powered off.

  4. Store the scale adapter, its cable, and power supply somewhere safe.

Connect the scale to the Sunmi

  1. Unplug the scale's power cable from the USB wall charger.
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  2. Plug that end of the cable into the USB port on the side of the Sunmi. The scale draws its power from the Sunmi and turns on.
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Set up the scale in Cents

  1. Open the Connections screen in the Cents app. When the pop-up appears, tap OK.
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  2. In the Scale section, set Connection type to Local, then choose your scale under Local scale type: Auto-detect, Mettler, Avery, CAS, or CAS PB.

    1. Use CAS for CAS BW and PW models, and CAS PB only for a CAS PB scale. If you're not sure, start with Auto-detect.

  3. Wait for the scale to show Connected.
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Test the connection

  1. Start a New Service Order as a test order.

  2. Put something on the scale.

  3. At the weight input screen, tap the scale icon.
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  4. Confirm the weight reading matches what's displayed on the scale itself.

Add a remote display or wall mount (optional)

To add a wall mount or a second screen that displays weight, contact Mettler Toledo toll-free at 1-800-786-0812:

  • Option 1: Make the base display remote with a 10 ft cable (part #30241062) and an adapter (part #30317848).

  • Option 2: Keep the base display at the base and add a separate remote display (part #30125729).

Troubleshooting

  • Scale won't turn on after you connect it? Make sure the USB cable is fully seated in the Sunmi's side USB port. The scale is powered by the Sunmi, so it only turns on once that connection is solid.

  • Cents shows the scale as not connected? Confirm Connection type is set to Local and that you picked the right Local scale type. If you're unsure of the model, switch to Auto-detect.

  • Weight reading looks wrong or won't update? Re-check the scale type (use CAS for CAS BW and PW models, CAS PB only for a CAS PB scale), then reopen the weight input screen.

  • Using an older cable? The cable must be USB-to-serial (RS-232) with an FTDI chipset. Cables without an FTDI chipset may not be recognized.

FAQ

Do I still need the scale adapter?
No. Connecting directly replaces the scale adapter entirely.

Which scales are supported?
Mettler Toledo, Avery, and CAS, including CAS BW, PW, and PB models.

What if I don't know my scale's model?
Start with Auto-detect under Local scale type, then confirm the on-screen weight matches the scale.

Can I add a second screen to show weight?
Yes, for Mettler Toledo scales. See the remote display options above.

Need assistance?

Feel free to text our Cents Support team at 888-302-8809.

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