# 4-20 mA / 0-10 V analog loggers

## Manual calibration

Efento 4–20 mA and 0-10 V loggers are factory-calibrated and provide accurate current measurements by default. However, if necessary, users may perform a manual calibration to further improve measurement precision. Calibration is carried out at four reference points (4 mA, 12 mA, 16 mA, and 20 mA for a 4–20 mA loggers and 1 V, 2 V, 6 V, 10 V for 0-10 V loggers) with a loop calibrator to supply the logger with a known, stable current / voltage.

To begin the manual calibration process, connect to the logger using the mobile application, then tap **three dots in the upper-right corner → Advanced → Calibration → Manual calibration**, select the channel you want to calibrate, and follow the on-screen instructions.

{% hint style="warning" %}
Perform manual calibration only if the current accuracy does not meet your requirements. Using a low-quality or unstable loop calibrator can degrade the logger’s accuracy by introducing incorrect reference values, resulting in poorer measurement performance.
{% endhint %}

## Calibration parameters

| Measurements Number | The number of samples used to calculate the average. The highest and lowest readings are ignored.         | Range: 3 to 32.                                                                          |
| ------------------- | --------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| Startup Time        | The time (in milliseconds) the device waits after powering the sensor board before starting measurements. | Range: 0 to 300,000 milliseconds.                                                        |
| Factor              | A multiplier used to convert the raw ADC reading into the final Voltage (mV) or Current (mA) result.      | Range: 0 to 4,294,967,295 (Note: this value is the real factor multiplied by 1,000,000). |
| Always on           | Keeps the power supply to the sensor board on constantly.                                                 | <ul><li>Disabled (uses Startup Time).</li><li>Enabled (ignores Startup Time).</li></ul>  |


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