Note that on 12 February 1979 the third cross-check was performed prior to
departing the supported unit's area, the standards are still within
tolerance, and the team chief can inform the unit commander that
certification of his equipment is valid.
On 16 February 1979 the team
arrived at the second supported unit on the itinerary; the temperature was
cold and it was raining.
The team chief directed that the standards be
turned on to allow additional time for warmup and stabilization. The fourth
cross-check was performed in the afternoon of 16 February 1979, and the
results as shown in table 3 were unfavorable. This cross-check showed the
standards to be unstable and not suitable for calibrating at that time. Now
which standard is out of tolerance? If we assume here that when the J-F 332
was cross-checked with the J-F 730A voltage reference bank that the cross-
check showed no significant deviation from the norm, then the J-F 887
differential voltmeter is the instrument out of tolerance. Since it cross-
checked in tolerance at the end of the last stop, no customer TMDE is
involved. A notation stating this will be made at the bottom of the cross-
check sheet from the J-F 887. Also the remedial action taken to have the J-
F 887 brought into tolerance will be noted. Example: Evacuated to AACL on
17 February, a substitute J-F 887 serial number 00111 picked up from tech
supply and returned to the team on 17 Feb.
The cross-check on the
substitute J-F 887 will then be shown on the cross-check record.
When a standard is found out of tolerance during a cross-check and is
subsequently red-tagged, the cross-check readings must be recorded in the
appropriate table.
The only exception permitted is when the standard is
inoperable. In such cases, the word INOPERABLE will be placed in the space
provided for the cross-check readings, and an explanation noted at the foot
of the cross-check table.
When a standard fails between required cross-checks, an entry will be
made in the next available column of the table, with the date of failure
discovery.
e. Table 4 is one example of the AC voltage standard cross-check. In
this case the H-P 745A AC calibrator was used as a reference source and the
DAQ 5703 digital voltmeter as the measuring instrument. Note in columns one
and two (table 4) that the reference AC voltage and frequency are specified.
This should indicate to you that two different parameters can be cross-
checked at the same time (AC voltage and frequency response or tracking of
the digital voltmeter).
f. The third cross-checking example in this lesson is shown in Table 5.
You may note in this example that we can cross-check two different
instruments with only one reference monitor. The monitor in this case being
the H-P 334 distortion analyzer.
The first column in table 5 lists the
reference frequencies to be monitored and the columns under each instrument
list the maximum allowable percentage of distortion for each frequency.
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