Precision, Performance, Confidence. ™

2465 Piston Gauge - Negative Gauge Mode with a Manual Pressure Controller

The below content is from the 3990 Manual Pressure Control Pack Operator's Manual that is available at this link, Fluke Calibration Product Manuals

The content is specific to the 3990 Pressure Control Pack but also applies to older Pressure Control Packs. The 3990 Pressure Control Pack has valves and a schematic on it that make switching modes easier, and without breaking and switching tubing connections.

Also see the slides from this Webinar, Expanding Use of the PG webinar.pdf
Specifically, see slides 12 and 13, and slides 22 to 26 for negative gauge mode with a 2465 piston gauge and 3990 manual pressure control pack.

Vacuum (Negative Gauge) Mode
If the bottom of the piston is exposed to ambient barometric pressure, the top of the piston is used as test pressure. The test pressure must be lower than ambient pressure, and is referred to as a negative gauge or vacuum mode pressure. In practice, the bottom of the 3990-801 DWG piston is connected to the reference port of the device under test, and both the 3990-801 and the device under test are totally isolated from ambient pressure. Thus, the test port pressure is not truly a negative gauge mode pressure. Rather, it is a negative differential pressure referenced to a pressure that is very close to ambient, typically within about 0.25 kPa (0.036 psi) of current barometric pressure. Since both the DWG and the device under test are referenced to the same near-ambient pressure, the device under test responds only to differential pressure across the DWG piston.

Vacuum Mode (Negative Gauge) Operation
Please refer to Figures 1, 2, or 3, as appropriate.

  1. Verify that the mode valve is set to Vacuum (Negative Gauge).
  2. Verify that the bell jar is mounted on the deadweight gauge.
  3. Close the Test Port Vent valve and carefully open the Vacuum Supply valve to decrease pressure in the test port and in the DWG bell jar.
    a. Adjust the Vacuum Supply valve to achieve the desired rate of change in pressure.
    b. Close the Vacuum Supply valve once the pressure is close to the target value or the piston begins to float.
    c. Close the Reference Vent valve.
    d. Push to close the Equalize valve and rotate the Pressure Adjuster knob to adjust the final pressure and float position.
  4. If the Pressure Adjuster must be turned too many rotations to establish a floating pressure:
    a. Pull to open the Equalize valve.
    b. Open the Reference Vent valve, then use the Vacuum Supply or Test Port Vent valve to bring the pressure closer to the target value.
    c. Close the Reference Vent valve, push to close the Equalize knob and rotate the Pressure Adjuster knob to adjust the final pressure and float position.
  5. If the Pressure Adjuster knob will not rotate, it is probably at the end of its stroke. In this case:
    a. Pull to open the Equalize valve.
    b. Open the Reference Vent valve, then rotate the Pressure Adjuster knob in the opposite direction about 10 to 20 turns.
    c. Close the Reference Vent valve, push to close the Equalize valve and rotate the Pressure Adjuster knob to adjust the final pressure and float position.
Have more questions? Submit a request

Comments

Please sign in to leave a comment.