HF scientific DRT-100B Research Turbidimeters - Manual (Page 16)

Page 8 DRT-100B (5/00)
V. FEATURES INCLUDED WITH THE 20052 RESEARCH MODEL
(A) ADJUSTABLE SET POINT ALARM CONTROL
This feature provides “Dry” contact closure when the measured value exceeds a preset limit. In addition
to the dry contact closure, the DRT-100B has a red lamp on the front of the unit that illuminates when the
current NTU readings exceed the alarm limit. This limit can be set by placing the three position “ALARM”
switch labeled “SET’, “OFF”, “NORM” to the “SET” position. The potentiometer behind the face plate
is then adjusted through a hole in the face plate until the digital display shows the desired value. The
“ALARM” switch is then returned to the “NORM” position. At anytime, the alarm limit currently set in
the instrument may be determined by moving the “ALARM” switch to the “SET” position and reading
the digital display.
Three terminals (“NC”, “C”, “NO”) are located on the rear panel and are used to connect the user’s alarm
circuit. These contacts are rated at 5 amps at 110 VAC, 2.5 amps at 230 VAC. The switch may be set to
“OFF” to deactivate these contacts during Standardization or Calibration to prevent false alarms.
(B) RECORDER OUTPUT, 0 - 1 MA
This output is obtained through the mini-phone jack marked “0 - 1 mA” on the rear panel of the instrument.
(Mating plug supplied in accessory kit).
(C) FLOW-THRU UNIT FOR CONTINUOUS MEASUREMENT
This feature allows the continuous measurement of the turbidity of a process. The cell will accept a maxi-
mum pressure of 60 p.s.i., and a maximum flow rate of 1.5 U.S. g.p.m. The speed of response to a change
in process turbidity will, of course, depend on the length of the tubing connecting the measuring head to the
process, and therefore this tubing should be kept as short as possible.
Should air or gas bubbles be present in the tubing from the process, the Flow Clamp (Part #50004) should
be placed on the effluent tubing and adjusted to provide enough back pressure to eliminate all bubbles.
The EPA recommends that cuvettes used for instrument calibration, standardization or sample measurement
be indexed. For quick indexing of the flow through cuvette a rotational flow through assembly with locking
collar has been installed.
To index your flow through cuvette, slowly rotate the flow head at least one revolution, while observing the
reading and locate the position of lowest reading. Without moving the flow head, press down the flow head
and turn the locking collar until the flow through assembly is securely locked in place.
(D) ATTENUATION MEASUREMENT
This feature may be used for measurements in excess of 1000 NTU’s. Set the “ATTN. - NTU” switch to
“ATTEN”. The instrument is now in the light attenuation mode and the side detectors are not in the circuit.
Relative measurements can now be made. Known samples should be compared to readings on the digital
display and a graph drawn that will allow the user to determine process values (e.g., p.p.m. suspended
solids) from readings on the digital display.