Current meter internal and external method selection - Database & Sql Blog Articles

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Method 1: Error Method

The current meter internal connection method R measurement = Rx + RA, the error is the current meter partial pressure, the measurement result is too large, the relative error is RA / Rx; the current meter external method R measurement = RxRV / (Rx + RV), the error is the voltmeter The shunt is small, and the relative error is Rx/RV.

This method is suitable for roughly knowing the resistance value to be measured and the resistance value of the voltmeter and ammeter.

Method 2: Heuristics

The ammeter is measured once by the internal connection method and the external connection method. The counts of the voltmeter and the ammeter are changed. The relative sizes of the changes of the two tables are compared ΔI/I and ΔU/U, where I and U take a set of measurements. value. Analyze one of the larger causes and then evade. For example, △I/I>△U/U, indicating that the two connections have a great influence on the current, the reason is that the voltmeter partial pressure action is clear, and should be avoided in the experiment, so the current meter internal connection method should be used at this time.

This method is suitable for not knowing the resistance value to be measured and the resistance value of the voltmeter and ammeter.

Method 3: Precise method

The current meter internal connection method R measurement = Rx + RA, the current meter external connection method R measurement = RxRV / (Rx + RV), if the exact internal resistance value of the voltmeter or ammeter is known in the experiment, the internal resistance value of the electric meter can be substituted into the measurement result conversion A more accurate resistance of the resistor to be tested. At this time, it is not limited by the error size of the first method, as long as the connection method capable of measuring the exact value of the resistance can be selected.

This method is suitable for knowing the resistance value to be measured and the accurate value of the internal resistance of the voltmeter and ammeter.