Fluke 721 Dual Sensor Precision Pressure Calibrator

Overview

The Fluke 721 Precision Pressure Calibrator is a handheld instrument with two isolated pressure sensors, built for applications where static and differential pressure must be measured at the same time. Fluke designed it as a tool for gas custody transfer work: one calibrator reads the low differential pressure across a primary flow element on one sensor and the line static pressure on the other, and an optional Pt100 RTD probe adds the gas temperature. With 0.025% of full scale accuracy on both sensors, it gives metering technicians the reference they need to verify the inputs that a flow computer uses to calculate billed volume.

Seven Star LLC supplies the Fluke 721 to metering, instrumentation and calibration teams across the Sultanate of Oman and the GCC, with engineering support in Muscat. Gas transmission pipelines, fiscal metering stations, power plants burning pipeline gas and industrial users in the region all rely on periodic verification of differential pressure, static pressure and temperature transmitters, and Seven Star LLC helps those teams choose the right sensor combination.

Measurement Principle

Each sensor of the Fluke 721 is a stainless-steel pressure sensor connected to its own 1/8 in NPT port, and the two are isolated from one another so that different pressures can be applied simultaneously. The low-pressure sensor is either 16 psi (−14 to +16 psi, −0.97 to 1.1 bar) or 36 psi (−14 to +36 psi, −0.97 to 2.48 bar), with 0.001 psi resolution. The high-pressure sensor is chosen from seven ranges: 100, 300, 500, 1000, 1500, 3000 or 5000 psi (6.9, 20, 34.5, 69, 103.4, 200 or 345 bar). Accuracy is 0.025% of full scale for one year, except the 5000 psi sensor, which is specified at 0.035%.

Alongside pressure, the calibrator measures 0 to 24 mA with ±0.015% of reading ±0.002 mA accuracy and 0 to 30 V dc with ±0.015% of reading ±0.002 V, so a transmitter output can be compared directly against the applied pressure. With the optional 720RTD probe it measures temperature from −40 °C to 150 °C at 0.01 °C resolution, with ±0.25 °C combined uncertainty. There is no effect on accuracy between 15 °C and 35 °C; outside that band Fluke adds ±0.002% of full scale per °C.

Engineering Design of the Fluke 721

The housing measures 20 × 11 × 5.8 cm, weighs 1 lb 3 oz and is rated IP40. It runs on four standard AA cells for more than 35 hours of typical use, and operates from −10 °C to +50 °C. A large backlit graphic display can show up to three inputs at once, for example differential pressure, static pressure and temperature, and pressure can be displayed in any of 19 engineering units including psi, bar, mbar, kPa, kg/cm², several inH2O, mH2O and ftH2O references, mmHg and inHg. Five instrument setups can be stored for recall, and the unit starts in the last setup used.

The Fluke 721 includes an internal 24 V loop supply that can power a transmitter under test, and it can check the 24 V loop supplies in a control panel. Pressure measurement can be extended beyond the internal sensors by connecting one of 50 external Fluke 750P Series pressure modules, covering ranges from 0 to 1 inH2O up to 10,000 psi (2.5 mbar to 690 bar). The calibrator ships with a soft case, four AA batteries, a manual, test leads and a traceable calibration certificate. For hazardous areas Fluke also builds an intrinsically safe 721Ex version, certified Ex ia IIB T3 Gb under ATEX and IECEx, which omits the loop supply, V dc measurement and module connection.

Key Features

The Fluke 721 brings the following capabilities to pressure and metering work:

• Two isolated stainless-steel pressure sensors for simultaneous static and differential pressure measurement.
• Low-pressure sensor of 16 psi or 36 psi combined with one of seven high-pressure ranges up to 5000 psi.
• 0.025% of full scale accuracy on both sensors (0.035% on the 5000 psi sensor).
• Switch test function on both pressure inputs.
• Pt100 RTD input for temperature measurement with the optional 720RTD probe.
• 4 to 20 mA and 30 V dc measurement, plus a 24 V loop supply for powering a transmitter.
• Range extension with 50 external 750P Series pressure modules.
• Backlit graphic display for up to three readings and storage of five instrument setups.

Industrial Applications

On an orifice or other differential-pressure gas metering run, the Fluke 721 lets a metering technician verify the differential pressure transmitter, the static pressure transmitter and the temperature element in one visit, using one reference instrument. A typical site might have a differential pressure transmitter such as the Yokogawa EJA110E Differential Pressure Transmitter on the flow element and a static pressure transmitter such as the Rosemount 3051 Pressure Transmitter on the line. Beyond custody transfer, the dual sensors are useful for checking filter differential pressure, pressure switches and low-range draft or level transmitters.

Seven Star LLC supplies the Fluke 721 to customers in Muscat, Sohar, Salalah and across the GCC, and can advise on the right low and high sensor combination for each metering station. Teams that also need multifunction electrical sourcing, thermocouple simulation and documented HART procedures often pair it with the Fluke 754 Documenting Process Calibrator with HART.

Technical Specifications

The table below summarises the Fluke 721 specifications from the Fluke 721 and 721Ex technical data sheet.

How to Order

To order the Fluke 721, send an RFQ to Seven Star LLC stating the required low-pressure sensor (16 psi or 36 psi), the high-pressure range, and whether you need the 720RTD probe or 750P pressure modules. Our instrumentation division in Muscat will confirm availability and delivery across Oman and the GCC, and the technical datasheet can be downloaded from this page for engineering review.