BT-620 Manual
Page 37
BT-620-9800 Rev B
Time Period
Item
Manual Section
Weekly
Zero Count Test
8.1.1
Monthly
Flow Rate Test
8.1.2
Yearly
Annual Calibration
8.1.3
Table 1 Service Schedule
8.1.1. Zero Count Test
Air leaks or debris in the particle sensor can cause false counts which may result in
significant count errors when sampling clean environments. Perform the following zero
count test weekly to ensure proper operation:
1. Attach the zero count filter to the inlet nozzle (P/N 81754).
2. Configure the unit as follows: Sample Mode = 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.
8.1.2. 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 (P/N 81755). 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 1 CFM (28.3 LPM) ±5%.
4. The flow rate can be adjusted using the front panel (see Section 4.7)
8.1.3. Annual Calibration
The BT-620 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 specialized equipment and a skilled technician. Met One
Instruments maintains a calibration facility for calibrating particle counters according to
industry accepted methods such as ISO, JIS and NIST. The annual calibration also
includes inspection and preventative maintenance to improve product reliability.
8.2.
Flash Upgrade
BT-620 is firmware upgradeable via the serial connection using a Met One Instruments
flash burn program. Binary files and the flash program must be provided by Met One
Instruments.
