Q: What is causing the different sleep current values (found on the website data sheets and in the user manuals) and why is the “smallest” ML-525LE board drawing the “highest” sleep current?
Model Typical current Measured @ Voltage
ML-525SE <30uA 3.6V
ML-525LE <50uA 3.6V
ML-525PE <30uA 3.6V
The ML-525xx board factory test should read <100uA to pass the test.
It is the same value as the specification on a ML-x17 series board.
A: Sleep currents are extreme low. To perform a secure measurement, a special Microampère meter is needed, measurement is performed on the main board and therefore can’t be done by the customer or dealer.
And there is more what is causing differences…
The ML-525LE has an on-board BUK for the solar cell power regulator. It is integrated in the data logger power circuit and consuming a little extra power. Therefore, this model has the highest sleep current (<50 uA).
When a battery driven Power Board (with or without solar cell) is used on the ML-525SE /PE, the board will draw an extra, small amount of sleep current for the BUK in the power circuit. (Same situation as the on-board circuit on the ML-525LE). The power board sleep current is not seen in the ML-525SE /PE specs. This will only affect battery (and solar cell) driven systems.
Also, the primary (main board input) voltage is affecting the sleep current. Differences between battery (3.3V) and external power (4V) are significant. Typical: A higher voltage is drawing less current.
The factory test limit is set to a maximum of 100uA, matching the capabilities and precision of the factory test measurement equipment.