MIL-DTL-23919C(SH)
f. Resistivity shall be checked regularly during all product form testing (minimum once weekly) and distilled
water shall be added, as necessary, to maintain the required resistivity.
g. A minimum of 10 standard cells shall be placed in the standard tank for 96 hours at room temperature to
stabilize.
h.
All air bubbles shall be removed from the cell surface after immersion.
i. DC voltage measurement shall be conducted at the end of the stabilization period to determine the voltage
(potential) difference between 9 of the cells using the 10th cell as the base cell to measure against.
j. Three IVM, or equivalent, cells that measure within ±1 millivolt DC of each other versus the base cell shall
be identified to be used for further testing as standard cells.
k.
One of the three cells, called the base standard, shall be used to compare all product form cells.
l.
Other cells shall be maintained as spares in the event one of the standard cells fail.
4.5.2.2 Base standard reference cell failure. If the base standard IVM cell drifts more than ±1 millivolt DC
from the initial differential reading between any of the other standard IVM cells, the base standard will be replaced
by one of the other two Ag/AgCl standard cells as identified in 4.5.2.1.
4.5.2.3 Offset comparison test. The product form Performance A or Performance B cells shall be immersed in
a test tank of sufficient size to contain a minimum volume of water of 0.65 cubic feet (18.4 liters) per reference cell
to be tested and be of sufficient proportion to immerse the reference cells while also meeting the following criteria:
a.
Two inches (5.08 centimeters) of water below the lower cells shall be provided.
b.
Three inches (7.62 centimeters) of water above the uppermost cells shall be provided.
c. Sufficient space shall be provided to accommodate the minimum bend radius of the reference cell cable
between the reference cell and the tank wall, with the element face in a vertical position.
d.
A minimum of 8 inches (20.32 centimeters) between or in front of each reference cell shall be provided.
e. The transfer pump shall be capable of transferring the seawater to the test tank from the acclimation or
mixing tank in less than 10 minutes.
f. The standard tank and the test tank shall be electrically connected via a salt bridge containing 0.6 N NaCl
solution (equivalent seawater conductivity).
g.
The product form cells shall be allowed to stabilize for up to 2 weeks prior to environmental testing.
h. The test tank electrolyte shall be changed out to a new electrolyte on a daily basis during the stabilization
period.
i. After stabilization, the differential DC voltage (potential) between the Performance cells and the standard
shall be measured.
j.
The potential measurements shall be normalized to 68 °F (20 °C) per the following equation:
(
)
Enormalized = Emeasured + 0.33 × 20 - T@ Emeasured
where T@Emeasured is measured in Celsius.
4.5.3 Stability and static drift. Static drift is defined as the inherent deviation of potential versus standard from
the initial value over a period of time in which there have been no environmental changes.
StaticDriftn = E final - Einitial
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