GT-521S Manual Rev D
Page 26
8.
Maintenance
Due to the nature of the instrument, there are no customer serviceable components in
the GT-521S. The case of the GT-521S should never be removed or opened for any
reason.
Opening or removing the case of the GT-521S voids the warranty and
may result in exposure to laser radiation, which can cause eye injury.
8.1.
Service Schedule
Although there are no customer serviceable components in the GT-521S, there are
service items which ensure the proper operation of the instrument. The table below
shows the service schedule for the GT-521S.
Time Period
Item
Manual Section
Weekly
Zero Count Test
Monthly
Flow Rate Test
Yearly
Annual Calibration
8.2.
Zero Count Test
Air leaks or debris in the particle sensor can cause false counts which may result in
significant count errors when sampling in clean environments. Perform the following
zero count test weekly to ensure proper operation:
1. Attach zero count filter to the inlet nozzle (PN G3111).
2. Configure the unit as follows: Samples = SINGLE, Sample Time = 60 seconds,
Volume = Total Count (TC)
3. Start and complete a sample.
4. The smallest particle size should have a count <= 1.
8.3.
Flow Rate Test
The flow rate test verifies the sample flow rate is within tolerance. The reference flow
meter must be non-loading because the vacuum pump can be loaded down by external
restrictions. Met One Instruments sells a suitable flow meter (PN 9801). The flow rate
test follows:
1. Connect a ±3% reference flow meter to the sample inlet nozzle.
2. Start a 5 minute sample.
3. The flow meter reading after ~3 minutes should be 0.1 CFM (2.831 LPM) ±5%.
4. Adjust the flow rate if the error is > ±5% (see section 5.8).
8.4.
Annual Calibration
The GT-521S should be sent back to Met One Instruments yearly for calibration and
inspection. The annual calibration cannot be performed by the customer because this
calibration requires proprietary software and equipment and a skilled technician. Met
One Instruments maintains a calibration facility for calibrating particle counters
according to industry accepted methods such as ISO and NIST. The annual calibration
also includes inspection and preventative maintenance to improve product reliability.
