Testo 6721 Data sheet
Compressed air quality measurement
testo 6721 Dew Point Switch
The application
Stationary monitoring of trace moisture
in cooling dryers, membrane dryers
and pneumatic systems in the range
down to -30 °C
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The benefit
Extension of the life and increase in
reliability of the system, i.e. protection
from damage from corrosion, ice,
“water hammer” and material adhesion
due to high moisture in
compressed air lines
Alarm box with 2 alarm
LEDs (green/red).Connection to digital inputs of PLC
or other alarm (lamps).
Alarm box (((option)
Part no. 0554 6722
testo 6740 Series
The application
Reliable stationary monitoring of humidity in compressed air down to the dry
range of -45 °C
stream of a granulate, membrane or
adsorption dryer.
The benefit
Assures end product quality due
to dry air/compressed air. Protection of
the compressed air system and sensitive components from humidity damage
caused by corrosion, ice, “water hammer” and material sticking. This
extends the life of the system, and costly
process interruptions can be avoided.
. Installation down-
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The product
• Low-cost monitoring via 2
switch outputs
• Status display with optional
alarm box
• Easy operation via P2A software for configuration,
etc.
– Advanced humidity monitoring for compressed air down to -60°C
The product
• High reliability to -45 °C
due to asccurate and rugged Testo humidity
sensor
• Analog output 4 to 20 mA, plus
optional 2 switch outputs
• Compact design with
rotatable housing
through 350°
Instrument name Thread Display Part no.
testo 6741 G 1/2“ without 0555 6741
testo 6742 NPT 1/2“ without 0555 6742
testo 6743 G 1/2“ with 0555 6743
testo 6744 NPT 1/2“ with 0555 6744
– easy monitoring of humidity in compressed air down to -30 °C
Technical data testo 6721
/ -49 °F
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testo 6721
Part no. 0555 6721
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Measuring range -30 to +30 °C
Accuracy ±4 K (-30 to -20 °C
Sensor Testo humidity sensor
Process pressure max. 20 bar (abs) (290 psi)
Process temperature
Outputs 2 x switches potential-
Interface Mini-DIN interface (serial)
Voltage supply 2 0 to 30 VAC/VDC
(-22 to +86 °F
-22 to -4 °F
±3 K (-20 to -10 °C
-4 to 14 °F
±2 K (-10 to 0 °C
14 to 32 °F
±1 K (>0 °C
(with special trace humidity adjustment) and
NTC temperature sensor
0 to +50 °C (32 to 122 °F)
free max. 30 V/0.5 A
for parameterization /
adjustment / analysis via
P2A-Software
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Technical data testo 6740
Measuring range- -60 to +30 °C
Accuracy ±1K at 0 °C
Sensor Testo humidity sensor
Process pressure max. 50 bar (725 psi)
Process temperature 0 to +50 °C /
Outputs
Output parameters °CtA, °FtA, %RH, ppmv,
Voltage supply 20 to 30 VDC
(-76 to +86 °F
±3K at -20 °C
±4K at -40 °C
°C
(with special trace humidity adjustment) and NTC
temperature sensor
32 to +122 °F
2 x switches potential-free.
30 V/0.5 A (accessory)
1x analog: 4 to 20mA
(2-wire)
mg/m3, °C, °F
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/>32 °F
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/ 32 °F
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/ -4°C
/ -40
/
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Two-Pressure adjustment device for testo 6743
The application
In combination with the trace humidity
measuring instrument testo 6743, this
allows an adjustment (offset) to be
performed during operation.
The product
Up to now, the adjustment of pressure
dewpoint transmitters was generally carried out using a dewpoint mirror. This
requires time-consuming and expensive
measures such as deinstallation, aquisi-
The benefit
Ensures the stated measurement
accuracy over an extended period.
tion of a dewpoint mirror, comparative
measurements or even sending the
transmitter off to a 3rd party laboratory.
• Adjustment of the testo 6743
without instrument de-installation
• No reference instrument required
• Minimum time requirement
Testo has developed a low-cost alternative which uses the principle that different
pressure values result in different humi-
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Further information at
dity values. The 2-pressure adjustment
device is simply installed between the
process and the testo 6743. This
makes it possible to carry out
an accurate adjustment on
site – without a reference
measuring instrument.
2-pressure adjustment device
Part no. 0554 3314
Optimum application range: -40 C to 0 C .
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