Detection method of loop resistance tester:

1. Linear error of loop resistance tester

The linear error test and the indication error test are carried out at the same time. Within the measurement range, the percentage of the ratio of the maximum difference between the actual value and the ideal straight line to the full scale value is the linear error, and the linear error should not exceed the allowable error.

2. Stability and error of loop resistance tester

The stability error test is carried out in the smallest range of the tested loop resistance tester, and the wiring method is the same as that of the resistance indication error verification. The standard resistor is set at 90% of the minimum range of the tested loop resistance tester. Turn on the test switch of the tester. Within the measurement range, other conditions remain unchanged. The loop resistance tester reads uniformly within 1min within the specified measurement time. Take no less than 6 readings, and the maximum change of the indicated value of the verification point from the actual value should not exceed the allowable error of the instrument under test.

3. Resolution of loop resistance tester

The verification of resolution is generally only performed on the smallest range. Adjust the standard to a certain value R1, at this time the meter under test shows a certain value, then fine-tune the standard to make the last bit of the tested meter change by 1 word, and then read the standard value R2 of the standard, then twice The difference between the standard indication values Δ=|R1-R2| is the resolution of the meter under test. The resolution of the loop resistance tester should be compatible with the corresponding range, less than 1/10 of the accuracy level.

4. Working current of loop resistance tester

The verification of the indication error of the output working current of the loop resistance tester can adopt the resistance voltage method or the standard ammeter method. The loop resistance tester with adjustable current value should uniformly select 3 to 5 verification points between 10% and 100% of the range. The minimum rated working current of the loop resistance tester should be ≥100A. Because there is an oxide film between the switch contacts, if a smaller current is used for detection, the test result is generally much larger due to the influence of the oxide film, but the oxide film is under high current It can be broken down. Theoretically, as long as the test current does not exceed the rated current, the larger the better, but when the regulations were formulated, considering the production level of relevant domestic instruments at that time, it stipulated that the current should not be less than 100A.