The Fluke Model 7250 pressure calibrator / controller (formerly Ruska 7250) offers an economical approach to automatic pressure testing and calibration with a precision of 0.003 % of full scale for ranges to 2,500 psi (17.2 MPa). A 3,000 psi (21 MPa) full scale range is available with 0.012% of reading precision from 900 psi to 3000 psi (6.3 to 21 MPa) precision.Models 7250xi and 7250i offer advanced percent of reading precision for increased capability with a single instrument, reducing the investment required to calibrate a wide variety of pressure devices and ranges.The Model 7250xi provides 0.005 % of reading precision from 5 % to 100 % of the instrument’s range. This unmatched precision is achieved through unique quartz pressure sensing technology and multiple quartz sensors in a single instrument. Various ranges from 0 to 20 and 0 to 2 500 psi (0 to 140 kPa and 0 to 17.2 MPa) are available.The Model 7250i provides 0.005 % of reading from 25 % to 100 % of range and is available in various ranges from 0 to 5 and 0 to 2,500 psi (0 to 35 kPa and 0 to 17.2 MPa).
For pressure below the lower threshold of 5% for the 7250xi and 25 % for the 7250i, the precision becomes 0.005 % of the lower value. For example, a 1,000 psi (7 MPa) Model 7250xi provides 0.005 % of reading from 50 to 1,000 psi (0.035 to 7 MPa); the precision for pressures from 0 to 50 psi (0 to 0.035 MPa) is 0.005 % of 50 psi (0.035 MPa).
High-speed pressure control
All Series 7250 instruments up to 2,500 psi (17.2 MPa) reach setpoint in 20 seconds or less into a 15 cubic inch (245 cc) volume, with no overshoot, to allow high-speed pressure test and calibration.
Dual control modes
The Series 7250 also provides two user-selectable control modes: active and passive mode. In active mode, the 7250 is continually maintaining the setpoint and can compensate for small leaks and pressure changes due to temperature. In passive mode, the user defines a control band and the 7250 will turn off the controller once it achieves the setpoint within the control band. In a leak-free and temperature- stable system, passive mode contributes no additional uncertainty, providing optimum performance.
Automating pressure test and calibration
The 7250 is easy to use and can automate your calibrations in several ways:
Step up/down: for calibrations where the increments are fixed intervals, enter a userdefined step value. The Series 7250 increases or decreases the pressure by the step amount with the jog dial—no more lengthy keystroke sequences to program.
Sweep test: for simple exercising routines, as with dial gauges, enter a start value, a stop value, and number of times to repeat the cycle. The Series 7250 will automatically exercise the device under test prior to the calibration run.
Onboard programs: For frequently used or lengthy calibrations, the Series 7250 can store up to 20 user-defined programs/profiles with up to 1000 steps total in internal memory.
Computer interface: Every Series 7250 is provided with both an RS-232 and IEEE-488 interface, and Series 7250 syntax follows SCPI protocol for easy programming. A LabVIEW® driver is available as a free download. As a standard feature, software written for the previous generation Series 7215, 7010 and 6000 instruments is fully supported by the Series 7250. The Series 7250 can also be set to 510 emulation mode to use software originally written for the DPI 510. Firmware updates can also be performed over the RS-232 interface (updates can be downloaded from the web site). The 7250 series is compatible with COMPASS software.
Versatility to handle any pneumatic pressure calibration
The Series 7250 is versatile enough to handle almost any type of pneumatic pressure calibration.
Wide pressure range: available in a variety of standard or custom full scale pressure ranges from 5 to 3,000 psi (35 kPa to 21 MPa)
Pressure units/scales: Select from over twelve standard units of measure, including inHg at 0 °C and 60 °F, kPa, bar, psi, inH2O at 4 °C, 20 °C and 60 °F, kg/cm2, mmHg at 0 °C, cmHg at 0 °C, and cmH2O at 4 °C, and two user defined units.
Head pressure: Automatic correction for head pressure differences
Absolute mode: The 7250 offers three different methods to make absolute pressure measurements. The barometric reference option provides the most convenient method and is available on ranges 15 psi (1.0 bar) and higher. Alternatively, the vacuum reference option (not available on the 7250xi) allows the connection of an external vacuum pump to the reference port of the instrument. An onboard vacuum sensor monitors the reference vacuum and allows for automatic zeroing in absolute mode. This option provides the lowest overall uncertainty since it does not include the additional uncertainty of a secondary barometric reference sensor. For pressure to 50 psia (4 bar) permanent absolute models are also available.
Autovent and autozero: With few keystrokes, the Series 7250 will vent the test port to atmosphere or automatically zero itself (autovent is not applicable to permanent absolute models).
Protection of the device under test: Set upper and lower pressure limits to ensure protection of the device under test. ‘
The Series 7250 can be provided for gauge mode operation, or with:
- Optional vacuum (negative gauge) mode for bidirectional devices
- Optional barometric reference for absolute mode calibrations
- Permanent absolute ranges to 50 psia (4 bar) full scale which include a tare feature for simulated gauge mode operation
- COMPASS® for Pressure