Yokogawa EXA DC402 Dual-Channel Conductivity Analyzer - Manual (Page 70)

IM 12D08E02-01E
Appendix 10-7
10-8. USP <645> Water Purity Monitoring
What is USP?
USP stands for United States Pharmacopeia and it is responsible for issuing guidelines for the pharma-
ceutical industry. Implementing these guidelines is highly recommended for companies wishing to mar-
ket drugs in the US. This means that USP is important for pharmaceutical companies worldwide. This
new USP, aims at the replacement of 5 antiquated laboratory tests by simple conductivity analysis.
How have we accomplished this in DC402G?
1. In Software Rev. 1.1, (and later versions) we have defined an Error Code: E13. This is independent
of what range the customer is measuring or what temperature compensation method he is using for
water quality monitoring. When the display shows E13, then the water quality exceeds the USP limits,
and the FAIL contact closes to signal that the system needs urgent attention.
2. We have introduced uncompensated conductivity in the DISPLAY menu. In the LCD display the user
can read the temperature and the raw conductivity to compare his water quality with the USP table.
3. We have added a USP function to the contact allocation. All 4 contacts can be selected as USP
alarms. The contact closes when the USP limit is approached. It is possible to adjust a safety margin
for the water quality. For example, if the temperature is 64 °C. and the safety margin is adjusted for
20%, then the contact closes at 0.8 x 2.2 µS/cm. = 1.76 µS/cm. (2.2µS/cm is the USP limit at 64°C).
4. We have kept all the EXA functionality: It is even possible to have the mA Output and Display read-
ings in resistivity units. Most users will have very good water quality and in the resistivity mode they
will have better resolution on the recorder or DCS. The readings are simply the reciprocal values of
the conductivity values. In the example mentioned above the contact will close at an uncompensated
resistivity of 1/1.76 µS/cm. = 0.568 MΩ • cm.