43
AQUALAB
4. SERVICE
This section contains calibration and verification information, cleaning and maintenance
guidelines, troubleshooting steps, and customer support information.
4.1 VERIFICATION AND CALIBRATION
It is important to verify the AQUALAB water activity calibration against known standards to
guarantee optimal performance and accuracy. METER recommends verification daily, once
per shift, or before each use.
METER also recommends annual factory calibration to maintain optimal performance.
4.1.1 WATER ACTIVITY VERIFICATION
The AQUALAB uses the chilled-mirror dew point technique to determine water activity.
Because this is a primary measurement of relative humidity, no calibration is necessary;
however, METER recommends periodic verification. The components used by the
instrument to measure water activity are subject to contamination, which may affect
AQUALAB performance. Therefore, frequent verification assures that the AQUALAB is
performing correctly. In addition, providing a linear offset can be used to overcome any
additional instrument drift.
4.1.1.1. VERIFICATION STANDARDS
Verification standards are specially prepared, unsaturated salt solutions having a
specific molality and water activity value that are accurately measurable. The verification
standards that were sent with the initial shipment are very accurate and readily available
from METER. Using verification standards to verify accuracy can greatly reduce preparation
errors. Performance Verification Standards come in seven water activity levels: 1.000,
0.984, 0.920, 0.760, 0.500, 0.250, and 0.150 a
w
(Table 4). The standards are produced under a
strict quality assurance regime. Please contact Customer Support.
Table 4 Verication standards
Verification Standard at 25 °C
Dew Point a
w
Capcitive a
w
17.18 mol/kg LiCl 0.150 ±0.005 0.150 ±0.015
13.41 mol/kg LiCl 0.250 ±0.003 0.250 ±0.015
8.57 mol/kg LiCl 0.500 ±0.003 0.500 ±0.015
6.00 mol/kg NaCl 0.760 ±0.003 0.760 ±0.015
2.33 mol/kg NaCl 0.920 ±0.003 0.920 ±0.015
0.50 mol/kg KCl 0.984 ±0.003 0.984 ±0.015
Steam Distilled Water 1.000 ±0.003 1.000 ±0.015
NOTE: Safety Data Sheet (SDS) for these standards are available at sds.metergroup.com.
To Next Page
Loading...