【 Weak current College 】 with pointer multimeter capacitance of 】

In the home appliance repair process, the capacitor leakage or capacity changes caused by the fault is not uncommon and symptoms vary. General pointer multimeter and some digital multimeter measurement not capacitors, especially those with small capacitors, to repair a big inconvenience. Here, I'll give you an introduction to several small volume capacitance measurement method for reference.

Method: find a β l ≥ 250 of triode (requires less penetrating current), such as unable to find that you can use two types of transistors combined with a Darlington form, shown in Figure 1. Will be measured capacitance and received in the transistor's c-e knot (if you have polarity capacitor capacitance c received extremely positive electrode of the transistor), and then use multimeter R×10k retaining, the black table pen very received c, then e very red, see Figure 2, the observation of the degree of instantaneous swing meter. This method uses several known capacity of normal (high accuracy) of the test, record the table pin every time the instantaneous amplitude of the largest swing, l for processing calculations, figure out the dial on each compartment should represent the value of the capacitor, so as to be usable for subsequent reference. The capacitance is measured by the capacitance meter oscillations to compare with the reference rate to determine the capacitance is good or bad.
Method 2: looking for a high accuracy known capacity capacitor (voltage 250V above) and a self-coupled output voltage adjustable transformer, shown in Figure 3. Cn to known capacitors, capacitor Cx to be measured, connected after logging line power Cx and Cn's own divider, but be aware that power transformer output voltage after should not be greater than the pressure of the Cx. At this point, according to the formula Uo/Co/Cx Ux = extrapolated Cx capacity. If the pressure in the Cx 300V above, you can directly use the two-line capacitance received from 220V AC power source (Note: this method only adapt non-polar capacitors). Method 3: If the capacitor voltage 400V above and just estimating capacity, according to figure 4 connecting to the measured capacitance and multimeters one table pen thread, the multimeter to voltage block (250V) measuring AC voltage, so use multiple known capacitor test, remember table pin oscillations, which can provide a basis for estimating the capacitor in the future (Note: this method only for non-polar capacitors). Method 4: electrolytic capacitor. Because of the existence of polar electrolytic capacitors, as Figure 5 after another half-wave rectifier diode, according to the measured capacitance pressure appropriate to select auto-transformer output voltage. Co is a known capacity of electrolytic capacitors, capacitor cx to be measured, the measurement according to diagram wiring, according to the formula Co/Cx = U0/Uv can calculate Cx capacity.