Advanced Instruments Osmometer 3250 Service Manual

35
Power On Diagnostics Troubleshooting
Power On Diagnostics
Place a tube with saline or distilled water in the sample well. Turn on the instrument At “Press
START to Continue”, press START. The instrument performs a check of the cooling assembly
and the probes. If a Block Probe Failure, Sample Probe Failure or Cooling System Error
message displays, use the A/D tests to perform further testing.
A/D Tests
Note You must set the correct sample and block bin numbers before performing A/D tests.
1. Turn on the instrument. If there is a Supervisor/Operator keyswitch, turn it to the
Supervisor position (if required).
2. 2. Press TEST.
3. Press < or > to select A/D Tests.
4. Place a sample tube containing either isopropyl alcohol or a high value standard into the
freezing chamber, and press START.
The display will change to:
o° Blk NNNN.NN ohm
readout
(resistance or
temperature)
channel setting
(sample or block)
target temperature
(o°, +1 to -8)
5. Set the target temperature from +1 °C to -8 °C by pressing < sequentially.
6. Press > sequentially to read:
– Block probe resistance in ohms
– Sample probe resistance in ohms
– Block probe in degrees Celsius
– Sample probe in degrees Celsius, or Cooling block duty cycle (a % value).
Block probe resistance will indicate current temperature. The probe begins to cool after the
target temperature is set, and the resistance increases until it reaches the target temperature.
Sample probe resistance will indicate current temperature. The probe begins to cool after the
target temperature is set, and the resistance increases until it reaches the target temperature.
Due to thermal mass considerations between the positions of the block and sample probes,
the sample probe may be ± 0.5 °C of the block probe reading.
Duty cycle displays the percentage of time that the thermoelectrics power is on. When the
thermoelectrics begin to cool, the duty cycle is usually at 100%. As the instrument stabilizes,
the duty cycle decreases to around 60%.
Increased ambient operating temperatures do not affect the sample probe reading, but will
increase the observed duty cycle, up to 85% at the maximum temperature of 35 °C.
Variations in ambient non-condensing relative humidity have no effect on the sample probe
reading or duty cycle.

Advanced Instruments Osmometer 3250 Specifications

General

Brand	Advanced Instruments
Model	Osmometer 3250
Category	Measuring Instruments
Language	English