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80
GF 9950-10 Six Channel Transmitter
USP (United States Pharmacopeia) has de
fi
ned a set of conductivity values (limits)
to be used for pharmaceutical water. The standard requires that conductivity
measurement without temperature compensation be used for these applications.
The limits vary according to the temperature of the sample. The 9950 has the USP
limits stored in memory. It will automatically determine the proper USP limit based
on the measured temperature. Important Conductivity TEMP COMP must be set to
NONE and Unit Of Measure must be set to
μ
S.
Using the USP function
USP setpoints are de
fi
ned as a percentage below the USP limit, so a USP alarm
is always a HIGH alarm. The 9950 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 RELAY menu:
• RELAY MODE must be set to
USP
.
2.
In the INPUT menu:
• COND UNITS must be set to
μ
S
.
• TEMP COMP must be set to
None
.
Example:
• The water temperature is 19 ºC, so the USP limit is 1.0
μ
S.
• The USP PERCENT is set to 40%.
• The relay will be activated when the conductivity value reaches 40% below the
1.0 USP limit, or 0.6
μ
S.
• If the water temperature drifts to more than 20 ºC, the 9950 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 (0.66
μ
S).
Temperature
Range (ºC)
USP limit
(
μ
S)
0 to < 5
0.6
5 to < 10
0.8
10 to < 15
0.9
15 to < 20
1.0
20 to < 25
1.1
25 to < 30
1.3
30 to < 35
1.4
35 to < 40
1.5
40 to < 45
1.7
45 to < 50
1.8
50 to < 55
1.9
55 to < 60
2.1
60 to < 65
2.2
65 to < 70
2.4
70 to < 75
2.5
75 to < 80
2.7
80 to < 85
2.7
85 to < 90
2.7
90 to < 95
2.7
95 to < 100
2.9
100 to < 105
3.1
USP Limits
NOTE
: Relay will activate if USP limit is exceeded, Temperature Comp is set
to Linear or Pure Water, Conductivity Measurement is NOT in uS, or if
the Conductivity Sensor Electronics is indicating a measurement error.
Modbus
The 9950 Modbus Module allows the 9950 to be connected to a serial Modbus RS485
network. The Modbus Module will allow for PLCs and Scada Systems to query the current
readings, channel status, derived function values, state of the relay and 4 to 20 mA
outputs, along with status of the 9950 and Modbus communications. Detail programming
information is available in the 9950 Modbus Programming Manual.
Default Communication Parameters
ModBus Address 95
ModBus Termination
Off
ModBus Mode
RTU
ModBus Baud Rate
19.2K
ModBus Parity
Even
ModBus Endian
Big