Finglai SQ-72 Series

Contents

Finglai SQ-72 Series Analog Ammeter User Manual

Model: SQ-72 Series | Brand: Finglai

1. Product Overview

The SQ-72 series instruments are of the moving-iron type (for AC) or moving-coil type (for DC), featuring a square shape with overall dimensions of 72mm × 72mm. They are constructed with a flame-retardant ABS plastic case, a transparent glass window, and a printed scale dial, offering clear readings and an attractive appearance. They are widely used in industrial and mining enterprises, metallurgy, chemical industry, electric power systems, and various electrical control devices for measuring current in AC or DC circuits.

Front view of Finglai SQ-72 analog ammeter, showing the 'A' symbol for Amperes, a scale from 0 to 20, and the model 'Finglai SQ-72'. The needle points to approximately 10A.
Figure 1: Front view of the SQ-72 Analog Ammeter (10A variant shown)

2. Specifications

2.1. Technical Parameters

  • Accuracy Level: 1.5 level and 2.5 level
  • Range Specifications:
    • AC Direct Connection: 1A to 50A.
    • AC with Current Transformer (CT): 20A to 10kA / 5A (secondary current 5A or 1A).
    • DC Direct Connection: 1A to 20A.
    • DC with External Shunt: 20A to 10kA / 75mV (requires external 75mV shunt).
  • Resistance to Mechanical Forces: Can withstand 30m/s² wind; Impact frequency 80-120 times/min, 2h transport bumping
  • Dielectric Strength: 2KV 50Hz for 1min
  • Voltage Affection: The measured tolerance does not exceed base tolerance when the measured value changes by 15%
  • Work Position: Vertical
  • Operating Temperature: -20 to 40 °C (-4 to 104 °F)
  • Operating Humidity: 85% RH max, non-condensing

2.2. General Specifications

Parameter Value
Model Number SQ-72 Series
Accuracy Level 1.5 level and 2.5 level
External Dimensions 72x72 mm
Perforation Dimensions 67x67 mm
Matched Current Transformer BH-0.66-30 (for AC models requiring CT)
Matched Shunt FL-2 (for DC models requiring shunt)
Operating Temperature -20 to 40 °C (-4 to 104 °F)
Operating Humidity 85% RH max, non-condensing

For a visual representation of external and perforation dimensions, please refer to the official user manual PDF available at this link.

3. Setup & Installation

3.1. Wiring Guide

WARNING: All wiring operations must be performed with the power disconnected by a qualified electrician!

3.1.1. AC Ammeter Wiring

  • Direct Connection Type: Connect the meter directly in series with the circuit being measured.
  • Current Transformer (CT) Type:
    • Must be connected via a standard current transformer (CT).
    • Connect the meter terminals to the secondary side of the CT (typically 0-5A output).
    • CAUTION: The secondary circuit of the current transformer must NEVER be opened when the primary is energized, and one side of the secondary circuit must be reliably grounded.

3.1.2. DC Ammeter Wiring

  • Direct Connection Type: Connect the meter directly in series.
  • Observe Polarity: The terminal marked '-' connects to the negative side, the other terminal connects to the positive side.
  • Shunt Type:
    • Requires an external DC shunt (standard output is 75mV).
    • Connect the two current terminals of the shunt in series with the main circuit.
    • Connect the two leads (preferably specified leads) from the meter to the potential terminals of the shunt (+ to +, - to -).
Side view of the SQ-72 ammeter showing the two screw terminals for electrical connections and a zero adjustment screw.
Figure 2: Side view showing connection terminals
Back view of the SQ-72 ammeter showing the two main screw terminals and mounting points.
Figure 3: Back view showing connection terminals and mounting

4. Operating Instructions

4.1. Usage Precautions

  • Pre-power Check: Always ensure the wiring is correct and secure. For current transformer circuits, terminal screws must be tightened firmly to prevent poor contact, which can lead to heating or open circuits.
  • Matching Load/Transformers: If you are using a 150A ammeter, it will typically be marked "150/5A" or similar. This means it MUST be used with a 150/5 current transformer and cannot be directly connected to a 150A current.
  • Indication of Abnormalities:
    • If the pointer moves backwards (for DC meters): This indicates reversed polarity. Power off immediately and swap the two connections.
    • If the pointer pegs at full scale (hits the stop): This could be due to circuit overload, a mismatched CT ratio, or an open CT secondary circuit (for AC) generating high voltage. Power off and check immediately.

4.2. Maintenance

  • Regularly clean the meter glass surface with a dry cloth.
  • Check if the pointer rests on the mechanical zero mark when no power is applied. If not, gently adjust the "mechanical zero adjuster" screw located on the front of the meter case.

5. Troubleshooting

Fault Symptom Possible Cause(s) Remedy
No Indication (Pointer does not move)
  • No voltage/current in the circuit.
  • Loose wiring connection.
  • Open circuit in CT secondary.
  • Check if the circuit is energized.
  • Tighten the terminal screws.
  • Check the CT circuit.
Reading too high or too low
  • CT ratio or shunt rating does not match meter.
  • Damaged meter.
  • Verify CT ratio (e.g., 150/5 meter with 150/5 CT).
  • Replace with matching meter or CT/shunt.
Pointer vibrates excessively
  • Large fluctuation in the signal source.
  • Internal hairspring issue.
  • Check if it's normal load fluctuation.
  • Send for repair.
Pointer moves backwards
  • Reversed polarity (DC meter).
  • Phase sequence issue (AC - rare).
  • Power off and swap the two connections (DC).

6. User Tips & FAQ

6.1. User Tips

  • The SQ-72 ammeters generally provide precise and accurate measurements right out of the box.
  • Their light weight and straightforward design make them easy to handle and install.
  • Always double-check that you have the correct AC or DC model for your application, as they are not interchangeable.
  • Ensure all terminal screws are securely tightened to prevent poor contact and potential issues.

6.2. Frequently Asked Questions (FAQ)

Q: What are the physical dimensions of the meter?
A: The external dimensions are 72x72 mm, and the required panel cutout (perforation dimensions) is 67x67 mm.
Q: Is this ammeter for AC or DC current?
A: The SQ-72 series includes both AC (moving-iron type) and DC (moving-coil type) ammeters. This specific product listing offers various models for AC current (SQ-72-A) and DC current (SQ-72-DA). Please ensure you select the correct type for your application based on the model number (e.g., SQ-72-A for AC, SQ-72-DA for DC).

7. Warranty & Support

7.1. Warranty Information

This product is warranted against manufacturing defects for 12 months from the date of purchase under normal use conditions.

7.2. Additional Support

For further details, diagrams, or specific model information, please refer to the official user manual PDF available at this link.

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