Standard Output Signals of Electromagnetic Flow Meters

Standard Output Signals of Electromagnetic Flow Meters

Electromagnetic flow meters support multiple standardized output signals to meet industrial automation and process control requirements. The main standards include:

1. ‌Analog Signal Standards‌

4-20mA Current Signal‌

The most widely used industrial standard, offering long-distance transmission (up to 1000m) with strong anti-interference capabilities. 4mA represents the minimum flow, and 20mA represents the maximum flow‌.

0-10V/0-5V Voltage Signal‌

Suitable for short-distance transmission or low-voltage control systems, but prone to signal attenuation‌.

2. ‌Digital Signal Standards‌

Serial Communication Interfaces‌

RS-232/RS-485‌: Supports protocols like Modbus, HART, and Profibus for data exchange with PLCs or SCADA systems‌.

Wireless Transmission (e.g., GPRS)‌: Ideal for remote monitoring in hard-to-wire environments‌.

Pulse/Frequency Output‌

Pulse output: Each pulse corresponds to a fixed volume (e.g., 1L), used for cumulative flow measurement‌.

Frequency output: Proportional to flow velocity (0-5000Hz), suitable for control applications‌.

3. ‌Switch Signal Standards‌

Relay Output‌

Used for alarms (e.g., high/low flow, empty pipe detection) with typical ratings of 250mA/35VDC‌.

4. ‌Specialized Protocols‌

HART Protocol‌: Combines 4-20mA with digital communication for remote parameter configuration and diagnostics‌.

Fieldbus Protocols (Profibus, CANopen)‌: Used in high-speed industrial networks for real-time control‌.

5. ‌Signal Selection Considerations‌

Distance‌: 4-20mA is preferred for long distances (>100m), while RS-485 supports up to 1200m‌.

Interference Resistance‌: Current signals (4-20mA) outperform voltage signals in noisy environments‌.

For detailed technical specifications, refer to industry standards like GB/T 18659 for industrial process control applications‌.