Spirax Sarco M850 is a microprocessor-based, universal flow computer designed for the precise measurement of flow and heat in steam and water applications according to IAPWS-IF97, as well as other liquids and technical gases. The M850 series includes the panel-mounted M850-P and the wall-mounted M850-W, providing a flexible solution for industrial measurement and control systems. It integrates advanced math functions for energy balances, comprehensive process logging, and flexible display options.

Core Functionality

The M850 features a high-capacity internal 2 GB memory for results logging, capable of storing up to 250 files in a secure, encrypted text format. The 3.5" backlit TFT LCD display allows for digital, analog, tabular, or graphical visualization of process data.

• Measuring Channels: 12 available inputs including 6 analog (0/4-20mA), 3 RTD (Pt100/Ni100), and 3 pulse/binary inputs.
• Math Functions: 8 additional channels for calculated values such as flow balances, energy, and averages.
• Totalisers: Two independent totalisers per input, plus periodic and exceedance totalisers.
• Alarm & Control: 4 relay outputs assigned to alarm thresholds or pulse outputs.

Available Versions

Version	Mounting	Power Supply	Options
M850-P	Panel Mount	24 Vdc	0, 1, or 2 analog 4-20mA outputs
M850-W	Wall Mount	100/240 Vac	0, 1, or 2 analog 4-20mA outputs
M850-W-UL	Wall Mount	100/240 Vac	UL approved version

Technical Specifications

Analog Inputs (0 / 4-20 mA)

• Resolution: 18-bit A/C converter
• Accuracy: ±0.1% of FS (typical 0.05%)
• Isolation: 250 Vac continuous between signal and power

RTD Temperature Inputs

• Sensor Types: Pt100 x K, Ni100 x K (4-wire connection)
• Range: -200 to +850 °C (Pt100)
• Accuracy: ±0.5 °C (typical ±0.3 °C)

Pulse / Binary Inputs

• Frequency Range: 0 to 20 kHz (f < 0.001 Hz cut off)
• Modes: State monitoring, frequency measurement, pulse counting

Installation Considerations

Mechanical Installation

The M850 must be installed indoors. The wall-mounted version (M850-W) uses three fixing screws, while the panel-mounted version (M850-P) includes fixing clamps and an IP65 seal. Ensure sufficient clearance for wiring and display viewing.

Electrical Safety

Isolate the mains supply before opening the product. Functional earth terminals are provided for EMC compliance (sinking electrical interference) and must not be used as protective earth as the unit is double-insulated.

Failure Notification

Input or communication failures are indicated on the display using standard symbols:

• -F-: RTD sensor failure
• -II-: Current loop below 3.6 mA
• -E-: Current loop above 22 mA
• -S-: Steam parameters below saturation curve