RHE 21
Ex d Field Mount
An advanced function, explosion proof, field mount transmitter. With a corrosion resistant stainless steel enclosure and through-glass operation capability, the RHE 21 is rated to IP67 and suitable for the most extreme of installation environments. Features such as API Standard Volume correction and Net Oil calculation are available.
- Measure Mass Flow, Volumetric Flow, Density and Temperature
- Outputs 2 x Analog, 2 x Frequency/Pulse, 2 x Digital Status
- Inputs 2 x Digital, 1 x Analog
- PC USB for RHECom, RS 485 for Modbus RTU, HART over Analog
- Backlit Color LCD
- ATEX/IEC Ex, CSA approved
- Rheonik Assurance Factor®
General Specifications
Enclosure Material | Stainless steel. Optionally all 316L stainless steel |
Enclosure Rating | IP66 / NEMA 4X |
Ambient Temperature: | -40 to +60°C / -40 to +140°F (reduced visibility below -20°C / -4°F) |
Dimensions: | Depending upon construction type, please see Dimensions page (approx. 255 x 200 x 100 mm / 10 x 8 x 4 in) |
Display: | Backlit color LCD. Screen changes color to indicate warning or error |
Weight: | 8 kg (17.5 lb) |
Operation | 3 x behind-window capacitive buttons for menu navigation / settings |
Sensor Connection: | Integral sensor cable with 3m or 10m length or optional IS terminal box for separate custom length sensor cable connection |
Analog Outputs | Up to 2 x 4–20 mA outputs, active or passive Intrinsically safe versions available Uncertainty of analog outputs ±0.1% of reading, ±10 µA All analog outputs acc. to NAMUR NE43 |
Digital Outputs: | Up to 2 x configurable status outputs (IEC60946) Intrinsically safe versions available |
Pulse/Freq/Status Outputs | Up to 2 x configurable pulse/frequency/status outputs (IEC60946), max. 10 kHz |
Digital Inputs: | Up to 2 x configurable control inputs (IEC60946) |
Analog Input (optional): | 1 x 4 - 20 mA analog input (active) for two-wire external sensor |
Power Supply | 100–240 VAC (48 to 62 Hz), 5 W and/or 12–24 VDC ±10%, 4 W |
Digital Data Communications | Modbus RTU (RS485) Connection to PC (USB) with Rheonik RHECom software HART over analog output |
Cable Entries for Power and I/O | Two M16 x 1.5 entries with Ex e glands for 4–11 mm cables (standard) Optional ½″ NPT, ¾″ NPT, M20 x 1.5 or M25 x 1.5; versions with two ½″ NPT entries are also available (see datasheet) |
Hazardous Area Approvals | ATEX / IECEx and cCSAus (see datasheet) Others available on request |
Sensor and transmitter must have matching approvals (see datasheet).



