ZX21 series rotary resistance box for the DC circuit for use adjustable resistance, has a lower value of zero resistance, are all the most commonly used laboratory instruments for schools, factories and research units for electrical measurements and other experiments.<br><br>When you test with the item, please make sure the voltage is under 5V, and the current is under 50 mA. <br> The power is 0.25W<br> <br><b>Major performances </b><br> Made of high quality manganese copper wire, the resistance value does not change with the temperature, so that the resistance box is more accurate.<br> With high quality metal film resistors, it is more expensive than carbon film resistor, but it has good stability, little influence on temperature and high accuracy.<br> Better use knob switch designed according to customer needs<br><br> <b>Note:</b><br> 1.When the proper use of resistance box to rotate the knob in each group, so that the contact resistance is stable and reliable.<br> 2. The maximum allowable current value of the resistance box in use should never exceed the specified.<br> 3. When only a small change in resistance, then wire to the "0" and another small indication terminal, can reduce the resistance inside the lead resistance.<br> 4.The resistance box should be placed in shelter room, the air temperature +10℃~ + 40℃ , relative humidity below 80%, should not contain harmful impurities which can cause corrosion.<br><br> <b>Attention: </b><br> we will send the product to you as soon as possible <br> If you have any questions , please feel free to contact us <br>