This is a portable detection instrument specially used in hazardous environments such as underground coal mines. Its core task is to measure stray current and voltage on conductors such as rails, water pipes, and cable sheaths to prevent premature explosion of electric detonators or gas explosion accidents.
Based on current search information, I have compiled the core parameters, usage methods, and precautions for this instrument:
1. Core Functions and Features
Intrinsic Safety (Explosion-proof): This is its most important feature. The instrument usually has MA certification (Coal Mine Safety Mark), adopts a passive design (does not require power itself), ensuring absolute safety in flammable and explosive underground environments.
AC/DC Dual Measurement: It can measure stray current and voltage for both AC and DC separately.
Multiple Ranges: It typically has 20 range settings, covering from weak current to larger current ranges.
2. Main Technical Parameters (taking the common FZY-3 model as an example)
This instrument usually does not require batteries and works with a magnetoelectric meter head.
Table
Measurement Item Measurement Range (Range) Measurement Accuracy
Current Gear 0-50mA - 250mA - 1A - 5A - 10A DC ±2.5%
AC ±5%
Voltage Gear 0-0.2V - 1V - 4V - 20V - 40V Same as above
3. Usage Methods and Steps
To ensure accurate and safe measurement, please follow these steps:
Mechanical Zero Adjustment: Before use, adjust the screw on the meter head to make the pointer accurately point to the zero scale line.
Connect Test Leads: Tighten the wiring of the test rods (test leads) onto the two binding posts of the instrument.
Select Measurement Points:
Measurement points should be selected on different conductors (e.g., between rail and water pipe, between two rails, etc.).
The distance between measurement points is usually about 2 meters, or set a measurement point every 50-100 meters according to specifications.
Start Measurement:
Ensure good contact between the test rod probe and the measured object (the probe is usually made of hard alloy, and needs to be pressed firmly to remove the oxide layer).
Range Selection: If unsure of the current magnitude, start with the maximum range, then gradually decrease until the pointer deflection is moderate.
Read the Value: Place the instrument horizontally to ensure accurate reading.
AC/DC Cross Measurement: If AC stray current cannot be measured, switch to DC gear for testing, and vice versa.
4. Key Precautions (Safety Must-Read)
Large Current Protection:
When the measured current is >5A, only short-time measurement is allowed.
When the measured current is >10A, only instantaneous measurement is allowed.
Reason: Prolonged large current flow will burn out the internal shunt elements of the instrument.
Reverse Pointer Deflection: When measuring DC current, if the pointer deflects in the reverse direction, it indicates reversed polarity; swap the positions of the two test leads.
Voltage Conversion: Some models (such as FZY-3) use the current gear scale for voltage gear; the conversion relationship is usually: current value × 4 = voltage value (e.g., 50mA gear corresponds to 0.2V, 10A gear corresponds to 40V).
Storage: When the instrument is not in use, set the switch to the “Off” position (if available) or the maximum range gear to protect the meter head.
5. Common Models and Places of Origin
Common models: FZY-3, CZL1, etc.
Place of origin information: According to public information, Jiangsu Yangzhou (such as Yangzhou Kaier, Yangzhou Huateng, etc.) and Shanghai (such as Shanghai Shengxu) are the main production areas for this type of instrument. Considering your geographical location (Yangzhou), there may be local manufacturers or suppliers.
Although this instrument has a simple structure (passive), it is crucial for mine safety. When using it, be sure to strictly follow the principle of “instantaneous measurement for large currents” to avoid damaging the equipment.
