How to Wire a Dual-Display Ammeter in a Distribution Board

When installing a dual-display ammeter (measuring both voltage and current) in a distribution board,

 follow these steps and precautions:  

### **1. Installation Preparation**  

1. **Select a Suitable Location**: Drill an opening on the distribution board (size according to the meter

 specifications) to ensure stable installation.  

2. **Tools and Materials**: Prepare a screwdriver, insulating tape, current transformer (CT), terminal blocks,

 etc.  

### **2. Wiring Steps**  

#### **1. Current Measurement Wiring (Three-Phase Circuit)**  

- **Current Transformer (CT) Connection**:  

  - **Single-Phase Measurement**: Connect the CT’s S1 and S2 terminals in series with the phase wire 

being measured. Connect the ammeter’s corresponding terminals to S1 (+) and S2 (-).  

  - **Three-Phase Measurement**:  

    - Install a CT for each phase. Connect S1 to the "+" terminal of the ammeter for the corresponding 

phase and S2 to the "-" terminal.  

    - All CT S2 terminals must be grounded uniformly (for safety protection).  

- **Note**: The CT secondary side must never be open-circuited, as this can generate high voltage 

and damage equipment.  

#### **2. Voltage Measurement Wiring**  

- **Single-Phase Voltage**: Directly connect in parallel to the measured phase wire and neutral (L-N).  

- **Three-Phase Voltage**: Use a voltage selector switch to toggle between phase-to-phase voltages 

(line voltages).  

#### **3. Auxiliary Power Supply Wiring**  

- The dual-display meter typically requires an external power supply (e.g., AC/DC 24V or 12V). Connect

 to the marked "L," "N" or "+," "-" terminals.  

- If the measured voltage exceeds 30V, use a separate power supply to avoid damaging the meter.  

#### **4. Shunt Connection (for Extended Range)**  

- For measuring high currents (e.g., >10A), disconnect the internal shunt and connect an external shunt

 according to the manual.  

### **3. Precautions**  

1. **Polarity and Direction**:  

   - Connect CT S1 to the ammeter "+" and S2 to "-" to ensure current flows into the "+" terminal.  

   - Match the voltmeter’s positive/negative polarity with the power supply to avoid reverse

 connection.  

2. **Range Matching**:  

   - The CT ratio must match the ammeter range (e.g., a 50A/5A CT pairs with a 50A ammeter).  

3. **Safety Operations**:  

   - Power off before wiring to ensure no voltage/current is present.  

   - The CT secondary side must be grounded to prevent high-voltage hazards.  

4. **Avoid Ground Loop Interference**:  

   - If the circuit includes a constant-current module, ensure the ammeter has an independent power

 supply to avoid accuracy degradation due to shared grounding.  

### **4. Summary**  

1. **Three-Phase Ammeter Wiring**: Series-connect CTs to each phase wire, with S1 to the meter "+" 

and S2 grounded.  

2. **Voltage Measurement**: Connect in parallel to the measured circuit, paying attention to power

 polarity.  

3. **Independent Power Supply**: Use a separate power supply for high-voltage scenarios to ensure 

meter safety.  

Refer to the meter manual and distribution board wiring diagram. Have a qualified electrician perform

 the installation to ensure safety and reliability.  

Let me know if you need further adjustments!