7
8860 Dual Channel Conductivity/Resistivity Controller
0 to < 5ºC
0.6
5 to < 10ºC
0.8
10 to < 15ºC
0.9
15 to < 20ºC
1
20 to < 25ºC
1.1
25 to < 30ºC
1.3
30 to < 35ºC
1.4
35 to < 40ºC
1.5
40 to < 45ºC
1.7
50 to < 55ºC
1.8
55 to < 60ºC
2.1
60 to < 65ºC
2.2
65 to < 70ºC
2.4
70 to < 75ºC
2.5
75 to < 80ºC
2.7
80 to < 85ºC
2.7
85 to < 90ºC
2.7
90 to < 95ºC
2.7
95 to < 100ºC
2.9
100 to < 105ºC
3.1
The USP limit
(
μ
S) is:
When the
temperature
range is:
USP Limits
USP (United States Pharmacopoeia) has de
fi
ned a set of conduc-
tivity values (limits) to be used for pharmaceutical water moni-
toring. This standard requires non-temperature compensated
conductivity measurement be used to warn if the con ductance
approaches the USP limit. The limits vary according to the tem-
perature of the sample.
The 8860 has the USP limits stored in memory. It will automati-
cally determine the proper USP limit based on the measured
temperature.
Using the USP function
In the 8860, USP setpoints are de
fi
ned as a percentage below
the USP limit, so a USP alarm is always a HIGH alarm. The 8860
can be set to warn you if the conductivity approaches within a set
percentage of the USP limit.
The following settings and conditions are required for a USP
relay function:
1.
In the CALIBRATE menu:
• RELAY MODE must be set to
USP
.
• RELAY SOURCE must be
Chan 1 or Chan 2 Cond
.
• SOURCE UNITS must be set to
μ
S
.
2.
In the OPTIONS menu:
• The TC Mode of the USP channel must be set to
None
.
(Service tip: If a relay is constantly on when it should be off,
check the relay settings listed above.)
Example:
• The USP setpoint is 40%.
• The water temperature is 19ºC, so the USP limit is 1.0
μ
S.
• The relay will be activated when the conductivity value reaches
0.6
μ
S, or 40% below the 1.0 USP limit.
• If the water temperature drifts to more than 20ºC, the 8860 will
automatically adjust the USP limit to 1.1.
• The relay will now be activated when the conductivity value
reaches 40% below 1.1
μ
S, or 0.66
μ
S.
