Is the pressure tester you are using safe?

This article focuses on several principles of safety protection circuits used in withstand voltage testers, addressing safety issues related to the widely used withstand voltage testers in the industry and highlighting potential dangers to operators.

This article addresses safety concerns related to the widely used withstand voltage testers in the industry, highlighting potential dangers to operators. It focuses on the principles of incorporating safety protection circuits in withstand voltage testers.

The Trend: Enhancing the Safety of Testing Instruments is a Universal Consensus

With growing consumer safety awareness and manufacturers' increasing emphasis on product quality, safety testing has become almost universal during production to ensure product quality and safety. Global product testing agencies, such as TUV, UL, SGS, and CCC, also strongly emphasize and prioritize enhanced product safety, imposing stringent requirements. Products passing these agencies' safety certifications display corresponding safety marks.

However, these certification agencies and manufacturers often overlook a crucial aspect: the safety of the testing equipment used, i.e., whether the instruments used to test product safety are themselves safe, or whether operators are working in a safe environment during product safety testing.

For many years, one of the fundamental devices in product safety testing has been the electrical strength tester, or high-voltage tester. However, like many electronic devices today, these testers have undergone significant changes to handle increasingly complex electronic products. Modern microprocessors and software enable new safety features, including fast output shutoff speed, various fail-indication circuits, no-load current limit settings, and ground fault interruption (GFI) circuits. All these advanced safety features aim to protect operators and mitigate risks.

Dangers Posed by Traditional High-Voltage Testers

Traditional analog high-voltage testers offer minimal safety features. Their analog designs are not easily modified for safety improvements, and the cost of such modifications often deters manufacturers.

Some testers fail to shut off the high-voltage circuit when the current exceeds the trip setting. Instead, they incorporate a high-impedance transformer that limits the current. The voltage collapses, limiting the current to a short-circuit current, typically less than 15 mA. However, by current safety standards, this current level is quite dangerous. A current between 5 mA and 10 mA can cause numbness. Between 20 mA and 40 mA, muscle contractions can cause respiratory distress and suffocation. Currents between 40 mA and 70 mA lasting 1 second or more can induce ventricular fibrillation and potentially be fatal.

Setting the voltage and trip current on a traditional analog high-voltage tester requires adjustments while high voltage is present, using a load resistor and external ammeter to obtain the desired readings. The output is adjusted until the high-voltage circuit or alarm/buzzer activates, then shut off. This process is usually repeated several times.

Today, a key advantage of microprocessor-controlled circuits is the ability to perform settings without a load. All parameters can now be set via menu-driven software without high voltage. This makes current parameter setting safer and more precise than traditional methods.