The 7250 Sys multi-range pressure calibration system is a complete, turn-key systems ideally suited for the test and calibration of the following:
- Pressure sensors
- Pressure transducers
- Pressure transmitters
- Pressure switches
- Pressure gauges
The third-generation in multi-range pressure calibration systems
For over 35 years, Ruska, now under the name Fluke Calibration, has supplied multi-range systems for pressure sensor calibration, pressure transducer calibration, pressure transmitter calibration, pressure switch calibration, and pressure gauge calibration. These systems provided maximum performance over a wide pressure range and relieved the customer of the need to utilize internal resources to configure a comprehensive pressure calibration system.
These systems consisted of multiple pressure controllers multiplexed to a single test port with automatic range switching and included ancillary components required for operation, such as vacuum pumps for sub atmospheric pressure control and gas boosters for high pressure systems.
The 7250 Sys represents a significant advancement in performance and capability coupled with a size reduction and cost saving design. The 7250 Sys is based on the popular Series 7250 digital pressure controllers featuring the unique quartz sensor that provides unmatched precision and long term stability. The 7250 Pressure Controllers also utilize digital control valve technology that provides fast response pressure control with zero overshoot allowing separate repeatability and hysteresis checks of the device under test.
Three different 7250 Sys configurations are available depending on performance and pressure range requirements:
- Eight ranges to 1 000 psi (70 bar)
- Eight ranges to 2 500 psi (170 bar)
- Twelve ranges to 2 500 psi (170 bar)
Although each of the above configurations includes multiple pressure ranges and controllers, the 7250 Sys has a single point of operation featuring a color, Active Matrix display. The 7250 Sys can also be operated via PC with the included IEEE-488 interface.
All supporting subsystems, such as a vacuum pump, gas pressure booster, pressure regulators and power distribution are integrated into a single bay cabinet with easy access doors, cooling fans, and casters.
Performance and flexibility
The 7250 Sys multi-range pressure calibration systems provide a fully integrated and automated calibration solution for pressure sensor calibration that can include either eight or 12 pressure ranges for maximum performance over a wide pressure range.
The eight range system for pressures to 1 000 psi (70 bar) provides a total 2 sigma uncertainty of 0.01 % of reading from 3 psi (0.2 bar) to 1 000 psi (70 bar) based on a one year calibration interval. From 0 to 3 psi (.2 bar) the total uncertainty is a fixed error of 0.0004 psi (0.028 mbar) per year. Total uncertainty includes precision (repeatability, linearity, hysteresis, and temperature effects), span stability over one year, the uncertainty from the calibration standard and the uncertainty from National Institute of Standards and Technology (NIST).
For pressures to 2 500 psi (170 bar) two configurations are available. In the 8 range configuration, the total two sigma uncertainty is 0.01% of reading from 8 psi (0.5 bar) to 2 500 psi (170 bar). For pressures from 0 to 8 psi (0 to 0.5 bar), the total uncertainty is a fixed error of 0.001 psi (0.07 mbar). For maximum pressure range coverage and performance, a 12 range system for pressures up to 2 500 psi (170 bar) is available. This system provides a total two sigma uncertainty of 0.01 % of reading from 0.5 psi (35 mbar) to 2 500 psi (170 bar). For pressures from 0 to 0.5 psi (0 to 35 mbar), the total uncertainty is a fixed error of 0.00005 psi (0.003 mbar).
The 7250 Sys controls pressure to the commanded set-point in 30 seconds, or less, without overshoot, allowing separate repeatability and hysteresis testing of the device under test.
The digital control valve technology utilized in the series 7250 Sys provides the following control stability:
8 range 7250Sys to 1 000 psi (70 bar)
- 0.0006 psi to 60 psi (0.04 mbar to 4 bar )
- 0.01 psi from 60 psi to 1 000 psi (0.7 mbar from 4 bar to 70 bar)
8 range 7250Sys to 2 500 psi (170 bar)
- 0.0015 psi to 150 psi (0.1 mbar to 10 bar)
- 0.025 psi from 150 to 2 500 psi (1.7 mbar from 10 bar to 170 bar)
12 range 7250Sys to 2 500 psi (170 bar)
- 0.0001 psi to 10 psi (0.007 mbar from 0.7 bar)
- 0.0015 psi from 10 to 150 psi (0.1 mbar from 0.7 bar to 10 bar)
- 0.025 psi from 150 to 2 500 psi (1.7 mbar from 10 to 170 bar)
The 7250 Sys also offers passive control mode that allows the operator to define a control band—once the set-point is within the control band the system will automatically turn off the controller. In a leak free, thermally stable environment, passive mode contributes no additional control noise providing optimum performance.
Each of the three available configurations above is capable of controlling pressure from –14.5 psig (-1 bar) to full scale (FS) in gauge mode, and from 0 2 psi (13.7 mbar) to FS in absolute mode into a load volume up to 1 000 cubic centimeters (60 cubic inches). Sub-atmospheric pressure control is provided by the internal vacuum pump that is equipped with an auto-vent valve to prevent contamination of the system in the event of power loss and a muffler for quiet operation.
Internal pressure regulation
The 7250 Sys requires a single pressure supply from a nitrogen or clean, dry air source. The supply can accommodate up to 3 000 psi (200 bar) since the 7250 Sys includes pressure regulators for each individual range in the system. For systems that include the optional gas booster, a shop air supply is required.
Master system controller
7250 Sys system activity is monitored and controlled by a single master system controller (MSC). The MSC allows the operator to enter a desired set-point pressure in up to 12 different pressures units and seven different languages. Internally the 7250 Sys will automatically control the pressure and change ranges both upscale and downscale to provide the highest performance pressure measurement and control to the DUT.
The MSC provides the operator with an Active Matrix color display, and user friendly menus. Multipoint test routines can be programmed into the MSC for high volume pressure sensor calibration. The MSC also includes a jog/step mode function, useful for testing mechanical type devices. When the absolute mode is selected, or a negative gauge pressure commanded, the MSC automatically activates the internal vacuum pump to allow sub-atmospheric pressure control.
Alternatively, the 7250 Sys can be connected to a PC via the IEEE-488 interface. Syntax commands are based on the SCPl format and sample programs are included in the manual (optional MET/CAL driver is available).
Single test port and reference port
The 7250 Sys features a single test port to connect the device under test (DUT). All eight, or twelve ranges are automatically switched to the common system test port. The 7250 Sys also has a single reference port for the entire system. This can be left open to atmosphere, or for applications where the device under test is placed in a environmental chamber for combined pressure and temperature characterization, it can be connected to the chamber so that the DUT and 7250 Sys are referenced to the same ambient pressure. When the Vacuum Reference option is selected, a second vacuum pump evacuates the reference port for absolute mode operation.
The 7250 Sys includes one internal vacuum pump to allow sub-atmospheric pressure control for testing negative gauge devices and absolute mode devices. An optional DUT absolute zeroing mode is available that will directly connect the vacuum pump to the test port for absolute mode zeroing of the DUT. The vacuum pump is mounted on vibration isolators to prevent vibrations from being transmitted to the system components. The vacuum pump is automatically activated from the master system controller when a negative gauge pressure is commanded, or when the system is used in absolute mode.
The 7250 Sys can include an optional Gas Booster mounted in the bottom of the cabinet on vibration isolators. This option is highly recommended for 7250 Sys configurations for pressures to 2 500 psi (170 bar). The gas booster will boost a standard nitrogen or clean, dry air bottle to the required pressure for the system, even when the bottle pressure drops to 500 psi (35 bar), insuring maximum usage and efficiency of the gas bottle supply. When this option is selected, the 7250 Sys requires a shop air supply at approximately 100 to 120 psi (7 to 8 bar).
The 7250 Sys is provided in a compact 483 milimeters (19 inches) single bay cabinet with casters for easy positioning. Cabinets are equipped with ventilation louvers and fans to prevent excessive heat buildup in the cabinet. Internal components are easily accessible through rear doors and removable side panels.