DH Instruments PPCK PLUS, Operation And Maintenance Manual

Page: 47 / 150

PPCK+™ Operation and Maintenance Manual
Page 39
©2001 DH Instruments, Inc .
Entering a value of zero turns the HEAD function OFF. Entering a value other than zero
turns the HEAD function ON using the height entered. Pressing
[ESCAPE] returns to the
main run screen with no change to the current head setting.
The HEAD function is NOT range specific. The HEAD setting remains the same as ranges
are changed. Edits made to the head specifications are independent of range.
When the HEAD function is ON (head height not 0), the ON condition is indicated by an
<h> in the top line, right side of the main run screen (see Section 3.1.1). When the HEAD
function is OFF (head height 0), the <h> is not shown.
To change units of head height between inches and centimeters and to change the test
gas species, press [SPECIAL] and select <2Head> (see Section 3.4.2).
The reference height of the PPCK+ pressure
measurement is the middle of the PPCK+ TEST port.
The head height should be entered as a positive value
if the device or system under test is higher than the
PPCK+ and negative if it is lower.
3.2.8 [LEAK CHECK]

PURPOSE
To run an automated leak check routine using PPCK+’s measurement capability to
measure the total pressure change and average rate of change over a period of time;
to edit the leak check time.

PRINCIPLE
The Leak Check function is provided to assist in using PPCK+ to measure leaks by
measuring pressure changes.
The principle of the Leak Check function is the measurement of pressure increase
or decrease. The Leak Check function allows a leak check time to be set. The total
pressure change and the average rate of change over the leak check time are calculated
and displayed.
Changing the pressure in a test system causes adiabatic temperature changes in the gas
that need to have dissipated before a valid leak measurement can be made. In general, a
2 to 5 minute wait before running a leak check is adequate to allow the adiabatic
temperature change to dissipate sufficiently for valid leak measurements to be made.
However, stabilization time may be much longer as volumes and pressures increase.