New Generation Pressure Transfer Standards from DH Instruments, Inc.
 

DHI’s third generation pressure controllers and monitors introduce new measurement technology based on Digiquartz® pressure transducers.  Quartz Reference Pressure Transducer (Q-RPT™) Modules integrate a Digiquartz transducer into a rigid, mechanical assembly that protects it from undesired connecting stresses and includes micro-valves to support AutoZeroing, measurement mode changes and an overpressure Self Defense System (SDS™). 

To qualify for use in a Q-RPT module, each Digiquartz transducer  is individually evaluated and characterized by DHI using state of the art piston gauges.  A proprietary Q-RPT compensation model, derived from more than 15 years of DHI experience with thousands of multi-ranged quartz pressure transducers is applied to optimize the metrological characteristics needed in a transfer standard. 

Figure 1. PPC3 Pressure Controller/Calibrator

Standard and Premium class Q-RPT modules are available to best fit a user’s performance and budgetary requirements. Both classes feature % of reading measurement uncertainty down to 30% of the transducer’s span. The Premium class Q-RPT’s span can be turned down up to 3:1 while maintaining % of reading uncertainty down to 30% of the turned down span. A single RPM4 monitor can be configured with one or two Q-RPTs.

  Figure 2. RPM4 Reference Pressure Monitor

Open architecture allows a single PPC3 pressure controller system to include up to six Q-RPTs, one or two internal and up to four external in RPM4s. PPC3’s 50:1 pressure control precision turndown allows it to support a range as low as 2% of its full scale without significant added uncertainty due to pressure control.

The unique combination of open architecture, measurement turndown and control turndown offered by PPC3 and RPM4 are a new step forward in covering a very wide range of devices under test with a single calibration system.
 

Figure 3. Quartz Reference Pressure Transducer (Q-RPT) Module

To fully exploit the benefits of Q-RPT modules’ % of reading measurement uncertainty, and PPC3’s pressure control capabilities, both PPC3 and RPM4 include an AutoRange function. AutoRange provides the user with a simple, foolproof way, to optimize a controller or monitor for a specific range of operation. When beginning a test, the operator enters the desired measurement mode (absolute, gauge, negative gauge), the pressure unit of measure and the desired full scale. AutoRange then selects the Q-RPT in the system with the best specifications for the range and measurement mode, and adjusts all internal settings (display resolution, overpressure limits and alarms, ready/not ready criteria, pressure control limits) proportionally to the range. AutoRange takes the guesswork out of using a single system to cover a very wide pressure range and different measurement modes.
    

Figure 4. Automated Calibration System Using PPC3 Pressure Controllers

Both products include RS232 and IEEE-488 remote communications as standard. Automation is simple using off-the-shelf COMPASS® for Pressure software. PPC3 controllers cover gas pressure ranges from as low as + 2 kPa (0.3 psi) to 10 MPa (1500 psi). RPM4 is available up to 280 MPa (40 000 psi).

Author:   This article was submitted by DH Instruments.
DH Instruments
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Phoenix, AZ   85044-5318 USA
Tel: (602) 431-9100