Just Better Keeping the life of your pump User Manual

Page 6

background image

Information on Digital Micron Gauges Continued

Micron Difference

Micron Range



When a DV-22N comes in for repair, it is compared to a secured system set up
with a N.I.S.T. Certifi ed analog gauge (DV-6 Hastings). Usually starting around
(1)60-100 microns, then (2)200-350 microns, then (3)500-700 microns, then
(4)900-1000 microns. These ranges of vacuum are the most common that peo-
ple work with to determine deep vacuum. We have been comparing the DV-22N
to the N.I.S.T certifi ed gauge on a secured system for a number years and has
proven to be highly accurate in all four ranges of vacuum. The average accuracy
as stated earlier in this section has proven to be consistent against this measure.

Erratic Readings:

There are three issues involved in the dis-

cussion of erratic readings. One is the understanding of the gauge’s displayed
micron increments that was just discussed. The second involves the re-sampling
period. The third is the environment inside the system being evacuated. When
the DV-22N is turned on, the display will show “JB” and the sensor will start to
calculate the ambient temperature.

Once the gauge has fi nished calculating the ambient temperature, it will display
the number “1” if it is not introduced to a vacuum level of 9000 microns or less.

Information on Digital Micron Gauges

There are three main complaints that are stated on the returns that JB receives
from the DV-22N and DV-24N. First, “inaccurate readings”. Second, “erratic
readings”. Third, “will not hold a vacuum”. Each of these complaints involves
both the understanding of the gauge functions and the principles of vacuum.

Inaccurate Readings:

Please note, for the DV-22N and DV-24N we have

a stated accuracy that references AVERAGE accuracy. Thus, between 250 and
6000 microns the unit is +/-10% AVERAGE accuracy and between 50 to 250
microns it is +/-15% AVERAGE accuracy. This does not mean our gauge has a
large accuracy discrepancy.

The term AVERAGE is an important part of this accuracy description. The
number of increments displayed on the JB digital micron gauge between 50 and
250 microns are 97. Between 250 microns and 6000 microns, there are 232 in-
crements. If you take a comparison reading between the DV-22N and the MKS
Baratron master gauge at each of the increments displayed on the Digital micron
gauge the average accuracy would be +/-10% in one range and +/-15% the aver-
age in the other range. Also, the number of increments decrease from the lower
micron readings to the higher micron readings.

For example, from 250 to 300 microns there are 16 increments, from 650-700
microns there are only 7 increments, between 1000 and 1050 there are 4 incre-
ments, and between 4000 and 4500 there are 4 increments. So at 650 to 700
microns the gauge has the ability to show 650-658-667-675-680-685-690-695.
But at the micron range of 4000 to 4500, the gauge only displays 4125-4250-
4375. This is important because when the system has an actual micron level of
4260, the digital micron gauge will show a reading of 4375 because the thresh-
old for the lower value that the gauge displays, 4250, has not been reached.
Once that threshold has been reached, the gauge will display that lower value
of 4250. Because the readings in these higher micron ranges only need to show
the movement through them , the difference between 4375 and 4250 is of no
concern in reaching the ultimate vacuum desired. This is why the JB DV-22N is
designed with the most increments in range that are going to be the most critical
in determining if the system is ready for charging.

If you understand the size of a micron, then small differences in ranges is noth-
ing to be concerned about. For instance: