How to detect whether the heating tube is good or bad?

​Use the ohmmeter of the multimeter to measure two aspects:

1. The resistance of the two outgoing wires should be normal. For 220V, 1000W is about 48 ohms, 1500W is about 32 ohms, and so on.

2. The (insulation) resistance between any outgoing wire and the shell is more than a few megohms. Those who can pass the above two steps are good.

The multimeter is a relatively precise instrument. If it is used improperly, it will cause inaccurate measurements and is easily damaged. However, as long as we master the use and precautions of the multimeter and act with caution, the multimeter will be durable. When using a multimeter, you should pay attention to the following matters:

1. Do not turn the wrong gear when measuring current and voltage. If you mistakenly use the resistance gear or current gear to measure voltage, it is very easy to burn out the meter. When the multimeter is not in use, it is best to turn the gear to the highest AC voltage to avoid damage due to improper use.

2. When measuring DC voltage and DC current, pay attention to the "+" and "-" polarity and do not connect them incorrectly. If the pointer is found to be reversed, the meter rod should be replaced immediately to avoid damaging the pointer and the meter head.

3. If the magnitude of the measured voltage or current is unknown, the highest gear should be used first, and then the appropriate gear should be selected for testing to avoid excessive deflection of the meter needle and damage to the meter head. The closer the selected gear is to the measured value, the more accurate the measured value will be.

4. When measuring resistance, do not touch the naked ends of the component (or the metal parts of the two meter rods) with your hands to avoid the human body resistance being connected in parallel with the measured resistance, making the measurement result inaccurate.

5. When measuring resistance, if the two meter rods are short-circuited and the "zero ohm" knob is adjusted to the maximum, the pointer still cannot reach the zero point. This phenomenon is usually caused by insufficient battery voltage in the meter. A new battery should be replaced for accurate measurement.

6. When the multimeter is not in use, do not turn it to the resistance gear, because there is a battery inside. If you are not careful, it is easy to cause the two meter rods to touch and short-circuit, which will not only consume the battery, but also damage the meter head in serious cases.