HF scientific 19944 Triple Validation Turbidimeter - 0-100 NTU - Manual (Page 13)

TVT2 (5/02)
Rev. 1.7 (.pdf) 8
Power: The instrument is equipped with a 90-250 VAC, 50-60 Hz switching power
supply; please verify that the line voltage falls within these specifications. If the line
voltage does not fall within these specifications please consult with the HF scientific, inc.
Technical Services Department to determine the proper method for powering your
instrument.
While making your connections, refer to Figure 5. The cover of the field terminal box
may be removed, if desired, by removing the two plug-in connectors at the power supply
module and loosening the protective earth terminal on the cover. Please note that the line
voltage side of the power supply has a locking connector and must be squeezed to
remove it.
RS 485 (Bi-directional Optional): The RS 485 half-duplex (2-wire) digital interface
option operates with differential levels that are not susceptible to electrical interferences.
This is why cable lengths up to 3000 ft can be implemented. The last device on every
bus must be terminated with a 120 ohm resistor to eliminate the possibilities of signal
reflection on the line. Do not run RS 485 cables in the same conduit as power.
Ensure each instrument is not powered when connecting the RS 485 line. Connecting an
instrument while powered may cause the instrument to unnecessarily reset and proceed
through the power on checks.
Relays: The Alarm 1 and Alarm 2 relays are mechanical relays rated at 240 VAC 2A.
There is also a Sensor Alarm relay that is a mechanical relay rated at 24 VDC 1A. Please
note that the relays are labeled NO (Normally Open), NC (Normally Closed) and C
(Common). As these alarms are configured fail-safe, the normal condition is with power
applied and in a non-alarm condition. Operation of these alarms is covered in section 8.5
Configuring the Alarms.
4-20 mA: The 4-20 mA output is driven by a 12 VDC power source and can drive
recorder loads up to 450 ohms. This 4-20 mA output is isolated from line power and earth
ground. Do not run 4-20 mA cables in the same conduit as power. Operation of these
alarms is covered in section 8.6 Setting the analog Output (O/P).
Ensure each instrument is not powered when connecting the 4-20 mA line. Connecting
an instrument while powered may cause the instrument to unnecessarily reset and
proceed through the power on checks.
4.0 Normal Operation
This process turbidimeter allows you to measure the turbidity of your process water on-
line. The turbidity of the process water is reported in Nephelometric Turbidity Units
(NTU). Readings above 10 NTU (100 with range of 0-100 enabled) are outside the range
of this instrument.
During normal operation, the instrument will have the AUTO block highlighted with the
current scale displayed on the lower row of the display and the measured reading on the
upper row of the display (see illustration below).