MIL-DTL-38219 Turbine Fuel, Low Volatility, Jp-7This specification covers one grade of aviation turbine fuel designated as JP-7. This specification was thoroughly reviewed as a part of acquisition reform. While most of the requirements were converted to performance terms, due to the military-unique nature of the product and the need for compatibility with deployed systems, it was determined that not all requirements could be converted. The issuance of this specification as "detail" is not intended to constrain technology advances in future systems.

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MIL-DTL-38219D(USAF)

APPENDIX B

B5.2 Option 2. Replace the Existing Meter. This option is recommended, as there will be a small but significant

difference in the readings of the digital millivolt meter and the existing meter when Option 1 is used. Confusion

could arise with both meters operational.

B5.2.1 Remove the existing meter from the Mark 8A TDR. Connect the 1000-ohm resistor between the two leads

that were connected to the existing meter. Connect the digital millivolt meter in parallel with the 1000-ohm resistor.

With the existing meter removed, leads from the TDR to the digital millivolt meter can be brought out through the

front of the TDR, as there will be a 2-inch-diameter hole where the meter was located. If the digital millivolt meter

gives negative readings during calibration, reverse the leads that lead to the digital millivolt meter.

B5.3 It may be possible to find a suitable digital millivolt meter that can be installed within the TDR case in lieu of

the original meter. However, most digital millivolt meters are considerably deeper than the original TDR meter and

there may not be sufficient room to accommodate the new meter within the TDR case. It may be possible, however,

to obtain digital meters which have a detachable display that could be mounted on the front of the TDR with the

remainder of the digital meter located within the TDR case (if there is room) or attached to the side or back of the

TDR.

B5.4 Some users may want to connect the AC power input to the digital meter through the TDR on-off switch.

B6. CALIBRATION

B6.1 The calibration procedure for the digital millivolt meter is the same as for the original meter. The Low Cal and

the High Cal controls are used to adjust the meter readings to agree with the calibration tube ratings as before. Note

the greater sensitivity of the digital millivolt meter may cause some jitter, but this should only be in the tenth of a

millivolt (i.e., TDR unit) range.

B7. OPERATION

B7.1 Mark 8A Tube Deposit Rating Methods. See ASTM D3241, paragraph 9.2.

B7.2 Delta Spun TDR. With the digital millivolt meter, negative TDR readings are possible and the sign (i.e., plus

[+] or minus [-]) of the TDR rating must be recorded as well as the TDR value. The pretest rating must be

algebraically subtracted from the post test rating to obtain the Delta Spun TDR rating. The Delta Spun TDR shall be

determined along the length of the JFTOT tube from position 14 to position 56 at 2-mm increments. The largest

value shall be reported.