Spirax Sarco M850-W-x and M850-P-x flow computers provide flexible, easy-to-use measurement for accurately calculating the mass flow and energy of steam, gases, and liquids across a wide range of applications. Standard products fully comply with applicable European directives and can be supplied with marking on request. Manufacturer’s typicality test certificates and uncertainty certificates/inspection reports are also available when specified at the time of order.
Available Options
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M850-P: Panel-mounted, powered by 24Vdc.
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M850-W: Wall-mounted, suitable for 100/240Vac power.
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Analog output selection: Each option is available without a 4 - 20mA analog output, with one 4 - 20mA analog output, or with two 4 - 20mA analog outputs. Instrument versions are designated M850-X, where X represents -P (panel-mounted) or -W (wall-mounted), followed by -0 (without analog output), -1 (with one analog output), or -2 (with two analog outputs).
User Interface (Front Panel)
| Display type | Color LCD film, 3.5”, LED backlight |
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| Display size/resolution | 43.8 mm x 77.4 mm / 272 (RGB) x 480 px |
| LED indicator keypad | 3 dual-color indicator lamps (red/green; alarm, REC, and USB indicators) |
| Number of buttons | 19 |
| Input configuration | 6 x I (0 / 4 - 20 mA): WE1, WE2, WE3, WE4, WE5, WE6; 3 x RTD (4-wire): WE7, WE8, WE9; 3 x I / PULS: WE10, WE11, WE12 |
| Signal type | 0 - 20 mA or 4 - 20 mA |
| Transmitter connection | 2-wire passive transmitter (powered by M850) or active transmitter (current-source transmitter) |
| Input resistance | 95 Ω ± 10% (protected by a series PTC 50mA fuse) |
| Transmitter power supply | 24Vdc + 10%/-20%, maximum 22mA per channel (protected by a series PTC 50mA fuse and resistor) |
| A/D converter resolution | 18-bit (24-bit sigma-delta analog-to-digital converter) |
| 50 Hz / 60 Hz filter | Sinc3 digital filter |
| Damping (first-order low-pass filter time constant) | 2s/5s/10s/20s/30s/1min/2min/3min/5min > 0.01% of full scale |
| Measurement resolution | - |
| Accuracy (T amb = +25 °C / +77 °F) | ± 0.1% of full scale (typical resistance is 0.05% of full scale) |
| Temperature drift | Maximum ± 0.02% of full scale/°C |
| Maximum input voltage | ± 40Vdc; no; all inputs grounded |
| Input current isolation | - |
| Analog output, RS - 485 / 422, Ethernet current isolation | 250Vac continuous; 1500Vac for 1 minute |
| RTD type (3 analog inputs for temperature sensors) | Pt - 100 x K; Ni - 100 x K; K = 1…11 (K is the multiplier; for example, for Pt - 200, K = 2) |
| Sensor type | - |
| Measurement range | Pt100 x K: -200 … +850 °C / -328 … +1562 °F; Ni100 x K: -60 … +150 °C / -76 … +302 °F |
| Sensor interface | 4-wire (2-wire with bridge) |
| Wire resistance compensation | Automatic compensation, or manual compensation from -99.99 … +99.99 Ω |
| Maximum wire connection resistance | 50 Ω |
| A/D converter resolution | 18-bit (24-bit sigma-delta analog-to-digital converter) |
| 50 Hz / 60 Hz filter | Sinc3 digital filter |
| Damping (first-order low-pass filter time constant) | 2 s / 5 s / 10 s / 20 s / 30 s / 1 min / 2 min / 3 min / 5min |
| Measurement resolution | > 0.05% of reading or 0.1 Ω (TBV) |
| Accuracy (T amb = +25 °C / +77 °F) | ± 0.5 °C / ± 0.9 °F (typical ± 0.3 °C / ± 0.54 °F) |
| Temperature drift | Maximum ± 0.02 °C / °C / 0.036 °F / °F |
| Maximum input voltage | ± 40Vdc |
| Input current isolation | None; all inputs grounded |
| Analog output, RS - 485 / 422, Ethernet current isolation | 250Vac continuous; 1500Vac for 1 minute |
PULS Type (Binary/Pulse/Frequency)
| Measurement range | 0 … 20kHz (cutoff at f<0.001Hz) (with 0 … 1kHz filter jumpers J1/J2/J3 open) |
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| Minimum pulse width | 25 μs (with 0 … 1kHz filter jumpers J1/J2/J3 open) |
| Frequency measurement accuracy (at T amb = +25 °C / +77 °F) | 0.02% |
| Maximum input voltage | ± 40Vdc |
| Input current isolation | None; all inputs grounded |
| Analog output, RS - 485 / 422, Ethernet current isolation | 250Vac continuous; 1500Vac for 1 minute |
| Configuration (default): OC or contact open/closed | (Internal jumpers J4 / J5 / J6 ON) |
| Open-circuit voltage | 5Vdc |
| Short-circuit current | 5mA |
| Open/closed threshold values | 2.7V / 2.4V |
| Configuration: voltage input | (Internal jumpers J4 / J5 / J6 OFF) |
| Signal amplitude | 4 … 36Vdc |
| Open/closed threshold values | 2.7V / 2.4V |
| Input resistance | ≥10 kΩ |
| Flow and thermal energy compensation device | - |
| Calculation update rate | 1 s |
| Compensation device accuracy for steam, water, other fluids, or process fluids | Typical: up to ± 0.5% under favorable conditions (up to ± 2% under unfavorable conditions) |
4 - 20mA Analog Output (Optional)
| Number of outputs | 1 or 2 |
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| Output signal | Passive 4 - 20mA (requires external loop power) |
| Resolution | 16-bit DAC |
| Resistance (RL) range at U ∞ = 24V | 0 … 600 Ω |
| Minimum loop supply voltage | U CCmin = RL x 0.022 + 8 |
| Maximum loop supply voltage | 28Vdc |
| Accuracy (T amb = +25 °C / +77 °F) | Better than ± 0.2% of full scale/°C |
| Temperature drift | Maximum ± 0.02% of full scale/°C |
| Analog output current isolation, RS - 485 / 422, Ethernet | 2250Vac continuous; 1500Vac for 1 minute |
Binary Outputs (M850 - W - x)
| Number of outputs | 4 |
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| Output type | 3-terminal (COM, NO, NC) electromechanical relay |
| Contact rating (resistive load) | 85 … 250Vac / 30Vdc, 3A |
| Maximum switching voltage | 250Vac / 125Vdc |
| Maximum switching power | 750 VA / 90 W |
Binary Outputs (M850 - P - x)
| Number of outputs | 4 |
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| Output type | 2-terminal solid-state relay |
| Contact rating (resistive load) | 60Vac / Vdc, 0.1A |
| Maximum on-state resistance | 20 Ω |
RS - 485 / 422
| Transmission protocol | ASCII Modbus RTU |
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| Number of network nodes | 256 |
| Maximum line length | 1200m (depending on data cable quality and transmission rate) |
| Transmission rates | 1.2, 2.4, 4.8, 9.6, 19.2, 38.4, 57.6, 115.2 kbps |
| Parity control | Even, odd, none |
| Structure | 1 start byte, 8 data bytes, 1 parity byte, 1 stop byte |
| Internal termination resistance | Yes, activated by DIP switch |
| Maximum bus voltage | -9V … +14V |
| Minimum driver differential output voltage | 1.5V (RL = 54 Ω) |
| Minimum receiver sensitivity | 200mV |
| Short-circuit/thermal protection | Yes |
| Analog output current isolation, RS - 485/422, Ethernet | 250Vac continuous; 1500Vac for 1 minute |
Ethernet Port
| Transmission protocol | Modbus TCP, ICMP (ping), DHCP server, HTTP server |
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| Interface | Ethernet 10BaseT |
| Data buffer | 300 B |
| Open connections (simultaneous) | 4 |
| Connection type | RJ - 45 |
| LED indicators | 2 (mounted on the RJ - 45 socket) |
USB Port
| Socket type | Type A, compliant with USB standards |
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| Version | USB 2.0 |
| Recording format | FAT 16 (within limited range) |
Power Supply (M850 - W - x)
| Rated voltage | 100 - 240Vac; 50/60Hz |
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| Voltage range | 85 … 264Vac; 47 … 63Hz |
| Power consumption | Maximum 20VA |
Power Supply (M850 - P - x)
| Rated voltage | 24Vdc |
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| Voltage range | 18 … 36Vdc |
| Power consumption | Maximum 8W |
Terminals (M850 - W - x)
| Cable entry/terminal | Spring-loaded terminal block |
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| Conductor cross-section | Solid wire 0.2 … 2.5 mm²; stranded wire 0.2 … 1.5 mm²; stranded wire with ferrule 0.25 … 1.5 mm²; AWG 26 … 12 |
| Cable glands | 4 gas-tight M20 glands, 2 gas-tight M16 glands |
Terminals (M850 - P - x)
| Cable entry/terminal | Screw-type, plug-in terminal block |
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| Conductor cross-section | Solid wire maximum 1.5 mm²; stranded wire maximum 1 mm²; stranded wire with ferrule 0.25 … 1.5 mm²; AWG 30 / 14 |
Weight
| Model | Weight (kg, approximate) |
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| M850-W-x (wall-mounted) | 2.00 |
| M850-P-x (panel-mounted) | 0.75 |
Enclosure (M850 - W - x)
| Enclosure type | Wall-mounted, polycarbonate |
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| Protection rating | IP65 |
Enclosure (M850 - P - x)
| Enclosure type | Panel-mounted, polycarbonate resin 920 |
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| Protection rating | IP65 / IP20 |
Environmental Conditions
| Ambient temperature | 0 … +55 °C (32 … 131 °F) |
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| Relative humidity | 5 … 95% (non-condensing) |
| Altitude | ≤2000m above sea level (6562 in) |
| Storage temperature | -30 … +70 °C |
| Overvoltage category | III |
| Pollution degree | 3 (panel-mounted and wall-mounted, installed inside an enclosure) |
| LVD (safety) | Electrical safety EN 61010 - 1:2010 |
| EMC | Exempt EN 61326 - 1:2006 Table 2, EN 55011 and EN 55022; immunity to radiated and electronic interference, Class B standard |
Safety Information, Installation, and Maintenance
For detailed information, refer to the installation and maintenance guide supplied with the product. Wall-mounted M850-W-x requires three fixing screws (not supplied) for installation on a wall or DIN rail; panel-mounted M850-P-x is supplied with fixing hooks. An adapter version is available as a separate kit for replacing an existing M200 or M800 flow computer with M850. This product is recyclable and, when disposed of correctly, does not present an environmental hazard.
How to Order
Example: 1-M850-W-1 wall-mounted flow computer, 4-20mA output, 240Vac.
Spare Parts
No spare parts are available for M850 flow computers. An accessory panel-mounted adapter is available.
