The Spirax Sarco M841 flow computer is designed to operate with the ILVA pipeline unit to measure various media, including steam, water, and compressed air. It provides density compensation for saturated and superheated steam based on pressure or temperature inputs, displaying accumulated flow, instantaneous flow, temperature, pressure, and density. It offers both wall-mounted and panel-mounted installation options to suit different industrial setups.

Key Features

• Suitable for steam, gas, and liquid applications.
• Automatically determines whether steam is in a superheated or saturated state based on temperature and pressure, obtaining density values from internal tables.
• Features automatic compensation for density, temperature, Reynolds number, and expansibility coefficient.
• 0.1 class accuracy with a high-definition color LCD.
• Includes functions for low-flow billing, steam stoppage detection, excess usage billing, power failure recording, and paperless recording.
• Automatically stores up to 65,536 groups of historical data (with adjustable intervals) and plots historical curves in full color for instantaneous flow, temperature, and pressure.
• Real-time clock and automatic scheduled meter reading simplify metrology management.
• Password protection prevents unauthorized personnel from altering preset data.
• Screen saver function extends screen lifespan.
• Non-volatile memory protects data during power failures for up to 10 years without requiring a backup battery.

Options and Installation

• Wall-Mounted: Features a stainless steel enclosure, weighing 8 kg. Powered externally by 220 VAC, internally regulated to 24 VDC. Installed using three M6 screws on a wall or pillar.
• Panel-Mounted: Weighs 2 kg. Standard 220 VAC power supply, with a 24 VDC option (must be specified when ordering). Installed on control panels or existing cabinets using two included mounting brackets.

Dimensions

Technical Specifications

Input Parameters

Signal Type	Parameter	Specification
4–20 mA (Diff. Pressure / Pressure)	Power Mode	Active input (M841 powers the sensor)
	Input Impedance	100 Ω
	Power Supply (Max)	100 mA
PT100 (Temperature)	Measuring Range	-200 to 560°C
	Accuracy	±0.3°C (at t ≤ 300°C); ±0.1% (at t > 300°C)

Output and Communication

Item	Specification
4–20 mA (Flow Re-output)	Active output (M841 provides power) Load Impedance (Max): 600 Ω Data Update Cycle: 0.5 s
Communication Interface	EIA RS-485 (standard) or RS-232 serial (optional), optically isolated
Communication Protocol	Baud Rate: 9600, 4800, 2400, or 1200 bps (selectable via panel) Format: No parity, 8 data bits, 1 stop bit Transmission Medium: Twisted pair

Power and Environmental Conditions

Item	Specification
Power Supply	85-264 VAC, 50 Hz ± 5%
Power Consumption	5 W
Operating Temperature	0 to 50°C
Relative Humidity	0 to 85%

Note

If using a UPS power supply, it is highly recommended to install a 10 VA isolation transformer in the power circuit to prevent high-frequency signal interference.