As with any electronic device, sometimes you may encounter issues with the TDS Meter.
Please follow the steps below to resolve your issue.
1. Did you remove the cap? (Applicable for digital only)
2. Have you turned it on? (Applicable for digital only)
3. Have you been storing it in the fridge? If so, sometimes you need to allow it to warm up to room temperature so that it can function properly. If you have already done so, check to be sure it hasn't shorted out due to water contact.
4. Please check the LCD screen to see if you see rust. If rust is present you will need to replace the TDS Meter.
5. If nothing else is wrong, the battery is probably dead. To replace the battery, remove the end of the TDS Meter and replace with a new 357-A battery that you can buy anywhere you get a watch battery from.