Once switching on the circuit and the pointer becomes steady, we can start taking the reading.
- Check the Range and Zero Position
Before reading the value, make sure the pointer is at the zero mark on the dial. If it deviate from zero, use the small zero-adjust screw on the side of the meter (usually marked Z or ZERO) to bring it back to 0. Otherwise, Otherwise, a systematic error will occur in the measurement.
- Read the Needle Position
Look at where the pointer is pointing on the scale and record the value. Since the needle often falls between two marks, we usually need to estimate the value.
Method 1: Linear Estimation
If the pointer is between 7 and 8 and closer to 7, the reading might be about 7.2 or 7.3. A common approach is to estimate how far the needle is from the lower number. For example, if it’s about one-third of the way from 7 to 8, the reading would be roughly 7 + 1/3.
Method 2: Rounding Down
If we want a conservative estimate, or if the needle sits exactly between two numbers (like 7.5), you can record the lower number (7). However, this method may make the reading slightly lower than the actual value.
- Convert According to the Selected Range
Analog meters usually have several ranges (like 10 V, 50 V, or 250 V). The scale printed on the dial is often fixed (for example 0–250), and the pointer position is proportional to the selected range. After obtaining the pointer value, it must be converted according to the currently selected range.
*Procedure: Read the value indicated on the scale (for example, 7.5), then multiply it by the ratio between the selected range and the full-scale value of the dial.
*Example: If the dial scale is 0–250 and the pointer indicates 7, selecting the 250 V range results in a reading of
(7/250)×250=7 V(7/250) × 250 = 7\,V(7/250)×250=7V.
If the 10 V range is used, the reading becomes
(7/250)×10=0.28 V(7/250) × 10 = 0.28\,V(7/250)×10=0.28V.
