Fluke 721Ex precision pressure calibrator with dual isolated pressure sensor is the ideal tool for gas custody transfer application allowing you to take simultaneously static and differential pressure measurements with a single tool. Fluke 721 Ex is the intrinsically safe version of the Fluke 721 and meets the standard for IECEx and Atex Ex ia IIB T3 Gb (Zone 1).

In our previous articles, we explain Fluke 721 Ex calibrator features, Fluke 6270 A calibrator, Fluke 726 Calibrator, Fluke 754 calibrator etc. In this article, we are going to explain you the Fluke 721 Ex Precision Pressure Calibrator interface & Calibrations.

Fluke 721Ex pressure calibrator

Fluke 721 Ex precision Pressure Calibrator Interface

For appropriate calibrations, we are going to explain to you the meaning of each & every functional key of Fluke 721 Ex Pressure Calibrator. Figure and Table shown below explains the location of the buttons, pressure controls, connection ports, and electrical inputs.

Fluke 721 Calibrator Functions:

[su_table responsive=”yes”]

Serial Number Function Description
Power Button used for switch on & off the Calibrator
Function buttons to configure the Calibrator
Push button for Zero pressure measurement
Backlight Push button to turn the backlight on & off
Common input
Input terminals to measure current and a contact closer to switch test
P1: Low-pressure port
P2: High-pressure port
RTD probe connector
Firmware programming connector for factory use only
Battery cover


Fluke 721 Ex precision Pressure Calibrator Procedure:

Fluke 721 Ex pressure calibrator is used for pressure calibration, temperature calibration, and pressure to current transmitter calibration. Here we explain its procedure of calibration step by step.

(A) Pressure calibration:

Set up of Fluke 721 Ex precision Pressure Calibrator for Pressure calibration:

  1. While switching on the calibrator make sure that all the three measurements i.e. P1, P2, and RTD all appears on the screen.
  2. If you only see two measurements display on the screen then press F1 (P1/P2) button until third one appears on the screen. If you see three measurements on the screen but not [RTD] then press F2 until [RTD] appears.
  3. As per your requirement set the upper display (P1), middle display (P2) and bottom display (RTD) to use psi and °F as the engineering unit.
  4. While vented to atmosphere as per your need, set both pressure displays to zero.
  5. Isolate the flow computer from the process.
                              Fluke 721Ex pressure calibrator Set up for calibrations

Pressure calibration is of two types; Static pressure calibration and dynamic pressure calibration. Have a look at its procedure.

(i) Static pressure calibration with Fluke 721 Ex Precision Pressure Calibrator:

  1. For the static pressure calibration, connect the high-pressure sensor input to the appropriate port on the flow computer or transmitter and a test-source such as a hand pump, nitrogen bottle etc.to the high-pressure terminal.
  2. The PC will instruct the user to apply one or more test pressures to the flow computer or transmitter.
  3. To generate pressure use, the high-pressure test source & enter observed data when called.
  4. When the process of calibration is completed, then carefully vent the system & disconnect the pressure source.

(ii) Differential Pressure Calibration with Fluke 721 Ex Precision Pressure Calibrator:

  1. This calibration is performed using atmospheric pressure as a reference, so the low-pressure connection of flow computer is vented & high-pressure connection on the flow computer is connected to the low-pressure port of the calibrator.
  2. Now make the Pc & flow computer to communicate through serial or USB port.
  3. The Pc will instruct the user to apply one or more test pressures to the flow computer or transmitter.
  4. Set the pressure mode of hand pump pressure/vacuum control & close the vent valve. Until the desired pressure is generated, squeeze the pump handle. For adjusting the pressure up or down, the fine pressure control of the pump can be used.
  5. When calibration process is completed, then open the pump vent control & disconnect the calibrator from the flow computer.

(B) Temperature Calibration:

Steps for temperature Calibration with Fluke 721 Ex Precision Pressure Calibrator:

  1. On the flow computer, the calibration of the temperature measurement is done with a single temperature point at the pipeline operating temperature.
  2. Insert the calibrator probe into the test thermowell.
  3. The main concept of this calibration is that the same temperature is measured at both thermowell &, therefore, the measured values should be same.
  4. When calibration is complete then remove the RTD from the test thermowell.

Fluke 721Ex pressure calibrator Set up of temperature calibration

(C) Pressure to current Transmitter Calibration:

Steps for Pressure to current Transmitter Calibration with Fluke 721 Ex Precision Pressure Calibrator:

  1. Connect the Fluke 721 Ex calibrator & pump to the transmitter as shown the figure below.
  2. Apply the pressure with the pump.
  3. Measures the current output of the transmitter.
  4. Ensure the reading is correct. If not then adjust the transmitter as necessary.

Fluke 721Ex pressure calibrator setup for Pressure to transmitter calibration

Well guys, hope this article seems to be very interesting for you. Have a look at it.

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