Choosing Between VOM and DMM for Voltage Measurement
What are the accuracy levels of VOM and DMM in voltage measurement? How can we calculate the error of reading by each device? Which one has a higher accuracy, and what are the possible error sources affecting the accuracy of VOM?
The VOM has a voltage reading of 19.4 V with a ±1% accuracy of 60 V full-scale reading. To calculate the error of reading by the VOM, we can use the formula: Error = (Reading x Accuracy)/100. Plugging in the values, the error of reading by the VOM would be (19.4 x 1)/100 = 0.194 V. On the other hand, the DMM has a voltage reading of 19.62 V with an accuracy of ±(0.5% reading +1 digit). To calculate the error of reading by the DMM, we can use the same formula. Plugging in the values, the error of reading by the DMM would be (19.62 x 0.5)/100 + 1 = 0.0981 V + 1 digit. Comparing the percentage errors, the VOM has a percentage error of (0.194/19.4) x 100 = 1%, while the DMM has a percentage error of (0.0981/19.62) x 100 = 0.5%. Therefore, the DMM has a higher accuracy compared to the VOM. Two possible error sources that make the VOM less accurate are internal resistance and calibration drift.
Accuracy Levels of VOM and DMM
VOM: Voltage reading of 19.4 V with ±1% accuracy of 60 V full-scale reading.
DMM: Voltage reading of 19.62 V with ±(0.5% reading +1 digit) accuracy.
Calculating Error of Reading
VOM: Error = (19.4 x 1)/100 = 0.194 V
DMM: Error = (19.62 x 0.5)/100 + 1 = 0.0981 V + 1 digit
Possible Error Sources Affecting VOM
1. Internal resistance: Higher internal resistance can affect the accuracy of VOM.
2. Calibration drift: VOM may drift out of calibration over time, leading to inaccurate readings.