Common Problems in High Resistance Measurements

High resistance measurement FAQs:
1. Why are there different readings with different resistance ranges when measuring the same object?
This is because to prevent the overvoltage from damaging the instrument when measuring the resistance, if the overcurrent occurs, the protection circuit in the instrument starts to work.
As a result, the test voltage is lowered to protect the internal amplifier. Measuring the same object at different voltages will have different results.
Also, if the reading is less than 199 when the resistance is measured, the accuracy will decrease if it is only three digits and the first digit is one. By
When measuring the resistance, when the first reading changes from 1 to a certain reading, the switch should not be turned to a higher range to prevent the instrument from being manufactured.
Too much current surge. In actual use, the accuracy of readings with less digits is less than the number of reading digits.
2. Why does measuring the current of some objects use different ranges and the measured results will differ greatly?
This is because the output current of a general object is not a constant current, and the instrument has a certain internal resistance if it is selected on the instrument.
The internal resistance is so large that the voltage drop on the instrument will cause measurement errors when it affects the output current of the measured object. The smaller the general current
The higher the internal resistance of the range, so the current should be used when measuring the current range. In practical use, as long as the ammeter has a reading
At that time, the small number of reading digits is more accurate than the number of reading digits.
3. Why is the reading of the instrument always unstable?
The general material does not have a very stable electrical current, which is exactly like a standard resistance sample, at a certain voltage. There are many materials.
In particular, the conductivity of antistatic materials does not comply with Ohm's law, so the readings are not stable during measurement. This is not the question of the instrument
The problem is determined by the performance of the measured object. Some standards stipulate that the reading of one minute of measurement shall prevail. Usually measured
Measurement accuracy at high resistance or micro-current is not good due to poor repeatability, requiring only 2 or 3 digits for measurement readings. In addition to measuring large electricity
If the shield is not good at the time of resistance, the external electromagnetic signal will cause unstable reading of the instrument measurement result.
4. Why must the power switch be turned off after the range switch is set to 10 again when the measurement is completed?
This is because the measured object and the input of the instrument have a certain capacitance during the measurement. This capacitor has been charged during measurement.
The value of the voltage at which the resistance is measured, if the instrument does not turn the power off after the 10th speed, the charged capacitor will be placed in the instrument.
The instrument discharges and causes damage to the instrument. When the measured capacitance of the object is larger, the higher the test voltage, the stored energy of the capacitor
The bigger the instrument is, the more likely it is to damage the instrument, especially if the instrument is very sensitive to the high range of the resistance or the low range of the current.
It is more likely to be damaged. So be sure to turn the range switch to 10 again before turning off the power.
5. Why don't you change the test voltage of the measured object while measuring the resistance?
If you change the test voltage of the test object during the measurement of the resistance, the voltage will increase when the voltage becomes higher or lower.
Pulsed current, this large current is likely to make the instrument over-range or even more damage to the instrument. On the other hand if the voltage suddenly changes
It can also damage the instrument by impacting the measuring instrument through the (distribution) capacitive discharge or reverse discharge of the object being measured. Have
The pressure resistance of the object is low. When you change the measurement voltage, there is a right breakdown and a large current damages the instrument. If you want to change the test
The amount of voltage, in order to ensure that the measured object will not breakdown due to excessive voltage, you must first dial the range switch to switch off after 104 files
Source, and then adjust the required voltage from the instrument's rear panel. Some materials are non-linear, that is, voltage and current are not in conformity with Europe.
According to Law, since the current does not change linearly when the voltage is changed, the measured resistance also changes.
6. Why did you turn off the power after the measurement switch is set to 10?
This is because the capacitors in the battery are charged with high voltage (up to 1200V or more).
The electrical energy is kept for a long time. If the power switch is turned off, the high-voltage capacitor inside the machine will be quickly discharged and will not be measured.
There is a dangerous voltage at the high voltage end that causes electric shock. If you only dial the power cord instead of turning off the power, although the power is off,
However, high-voltage capacitors in the aircraft may also sustain high voltage for a long time, which may cause electric shock or damage to people or other objects. When there is a problem with the instrument, do not open the case and cause electric shock due to high voltage inside the instrument. Find the instrument for professional technicians or send it back to the manufacturer for repair.

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