Measurement scheme of short-circuit current and open-circuit voltage

测量时首先要把太阳能电池板清理干净，放到阳光充足的地方正对着太阳，而且不能有仼何阴影投射在板面上。然后把万用表拨至DC一200V档即可测到开路电压值。然后把档位換成DC一20A的电流档，测量方法同上，就可以得到短路电流值。但这种测短路电流的方法仅限于太阳能电池板，其它电源或电池绝对不能用电流表直接测，否则有可能烧毁电源或仪表。

Since the internal resistance of an ammeter cannot be zero and the voltmeter cannot be infinite, there will be some errors when measuring directly with a multimeter. However, this method is simple and easy to use. Although there are some errors, it is sufficient for ordinary users. If you want to measure more accurately, you need an external power supply to offset the influence of the internal resistance of the instrument. The specific steps are as follows:

Figure 1 is a short-circuit current measurement scheme. The so-called short-circuit current refers to a state in which all the voltage drops caused by the power supply output current are added to the internal resistance r. The basic characteristic at this time is that the potential at point α = b = 0. After the external power supply is applied, the resistor R is adjusted to make the reading of the voltmeter V 0, which well simulates the state when the power supply is short-circuited. At this time, the reading of the ammeter A is the short-circuit current.

Figure 2 is a scheme for measuring open circuit voltage. The connection method is similar to Figure 1, except that the external power supply is reversed. By adjusting the external voltage, the ammeter A reading is 0, which is equivalent to using a voltmeter with an internal resistance of ∞, eliminating the measurement error caused by the internal resistance voltage divider of the voltmeter.

后面介绍的两种用附加电源测电流和电压的方法，也仅限于测太阳能电池板，不能用于其它电源，也不建议初学者操作，否则有可能烧毀电源或电池板。

The open circuit voltage and short circuit current of the solar panel are measured by the instrument. These are basic parameters and are available when leaving the factory. The open circuit voltage is easy to measure, that is, use the voltage range of the multimeter to directly measure the voltage of the solar panel without connecting the load. The short circuit current cannot be measured by the power supply load two-terminal method (Figure a), because the short circuit current is very large and will be affected by the internal resistance of the power supply and the internal resistance of the instrument, so it is inaccurate. The short circuit current must be accurately measured by the power supply load four-terminal method (Figure b). In circuit b, when the variable power supply is adjusted to make the output voltage zero, the short circuit current can be obtained.