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7.4.1.1 – Optical Calibration Check with Trico #DR7-FIL
Optical Calibration Checks are performed on the DR-7 optics using the neutral density films and
calibration tube purchased separately in the DR-7 Neutral Density Calibration test kit, Trico Part # DR7-
FIL. Following this procedure will check the optical sensors are within limits and the correct readings are
being obtained from the instrument. The test kit comes with three specific neutral density filters used in
the development of the DR instruments. Neutral density filters can vary in density range, use only those
filters provided in the test kit which have been specifically graded for the purpose of the DR calibration
check. Neutral Density films can vary due to manufacturing variances, and each kit should be measured to
establish its own set of calibration numbers. Follow the calibration guild provided with the Calibration
test kit to refine reading ranges.
NOTE:
Neutral density filters should be handled with care. Fingerprints, smears, or scratches will change
the calibration readings. Density filters from older model DR's can still be used on the DR-7. However,
note the changes in instrument reads in the table below.
Checking Optical Calibration:
1.
Make sure the Optics block and photocell area is clean and free of dirt and oil.
2.
Insert the glass Calibration tube (PN:43021) from the calibration kit into the optics by pressing the
lever forward on the left side of the optic block, lifting the gate and then sliding the calibration tube
into place.
3.
On the RUN DR tab press STANDARD and then START. Enter a false control number if needed.
4.
Insert a filter under the sensor area and quickly remove it.
5.
The screen will now say “Oil- Starting Test”. Wait for this message to change to “Waiting on End of
Oil” and then insert the filter under the sensors again and hold steady until the readings stop climbing.
6.
Record the reading.
7.
Repeat the same procedures for the two other density filters.
NOTE:
When inserting and removing density films, failure to remove films during sensor
zeroing will cause L and S reading to output 30 units lower than expected since sensors will zero
on the density filter.
Typical neutral density filter reading ranges for the L and S:
Filter Density L/ S Typical Mean Reading L/S Range
.10
35
31-42
.20
66
60-74
.30
89
81-98
Calibration Check Troubleshooting:
Issue
Reason
Solution
All density filter
values out of range
Values out of range <10 units
Recalibrate LED light source and recheck
Value out of range > 10 units
Optical sensor zeroed on density film, repeat
check following procedure
Recalibrate LED light source and recheck
Photocell detector faulty, replace photocell
Optics block out of alignment, consult Trico
Only one density filter
value out of calculated
range
Value out of range <10 units
Check density film for scratches, smears, or
fingerprints
