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


Stainless steel. Optionally all 316 stainless steel

Enclosure Rating:

IP66 / NEMA 7X

Ambient Temperature:

-40 to +60°C / -40 to +140°F (reduced visibility below -20°C / -4°F)


Depending upon construction type, please see Dimensions page

(approx. 255 x 200 x 100 mm / 10 x 8 x 4 in)


Backlit color LCD.  Screen changes color to indicate warning or error


8 kg (17.5 lb)


3 x behind-window capacitive sensors 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 4-20mA outputs, active or passive

Intrinsically safe versions available

Uncertainty of analog outputs +/- 0.1% of reading, +/- 10µA

Digital Outputs:

Up to 2 x configurable status outputs (IEC60946)

Intrinsically safe versions available

Pulse/Frequency Outputs:

Up to 2 x configurable pulse/freq. 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) or 12-24 VDC +/- 10%, max. 6W

Digital Data Communications:

Modbus RTU (RS485)
Connection to a PC (USB) with Rheonik RHEComPro software
HART over analog output

Cable Entries for

Power and I/O:

Type E* two M16 x 1.5 entries with Ex e glands 4-11mm (standard)
Type E3, E4, E5, EP optional ½” NPT, ¾” NPT, M20 x 1.5, M25 x 1.5

Type H* two ½” NPT

Hazardous Area Approvals:

For ATEX / IEC Ex and cCSAus please see Part Number Code page

Others available on request