One of the drawbacks of using a real time clock (RTC) in electronics is that temperature variations will make it gain or lose time over long periods of time. The real time clock (timekeeper) inside out our original data-logger used a standard watch chip that had an accuracy of +/- 20 ppm. Generally this is not such a big problem, but for multiple data-loggers in different temperature conditions, the clocks will drift apart and other techniques are required to synchronize the readings.
We introduced an "Extremely accurate" RTC into the data-logger product line last year (around 2016-03-24) with an accuracy of +/- 3.5ppm from -40°C to +85°C.
The new RTC is identified on the back of the meter with the model number suffix "-R1" as:
This model number can also be found using our UDM software.