DART SENSORS
FORMALDEHYDE SENSOR
This sensor is of the two-electrode electrochemical type, operating by the
diffusion principle and as such requires no external sampling hardware. In
the presence of formaldehyde gas a small direct current is produced; the
sensor requires no power supply of its own but this current requires
amplification to make it readable using external data collection
equipment.
ABSOLUTE MAXIMUM RATINGS
Parameter
HCHO Concentration
Temperature Range
Humidity Range
Service Life
Value
TBD
-10 to 40
15 to 90
3
Units
ppm
°C
%RH
years
SENSOR CHARACTERISTICS
Parameter
Output Signal
Resolution
Response Time (T90)
Baseline Offset
Repeatability
Linearity
Temperature Drift
Baseline Drift (20°C-40°C)
Calibration Stability
Min.
150
Typ. Max.
350
0.01
<30
<0.03
TBD
Linear
TBD
TBD
TBD
Units
nA/ppm
ppm
s
ppm
% of signal
%/°C
ppm
%/yr
NB: Sensor performance tested under standard conditions of 296K, 1atm., 50%RH. Sensors are best stored at room temperature in sealed plastic
bags for maximum storage life.
ELM HOUSE, 54 MARY ARCHES STREET, EXETER, EX4 3BA
TEL: +44 (0)1392 277733
e
-
MAIL: customer.service@dart
-
sensors.com
www.dart
-
sensors.com
Revised: 9th December 2013
INTERFERING SUBSTANCES
Substance
CO
H
2
S
H
2
SO
2
NO
2
NO
Cl
2
C
2
H
4
NH
3
CO
2
Ethanol
Phenol
Water vapour
SENSOR CHOICE
The sensor is available in two versions; the
standard sensor, and a variant offered for
compatibility where customers have previously
ordered the discontinued “premium” version of
the sensor. This variant is the “high catalyst
content” version.
Cross Sensitivity (%)
1
No data
0.1
12
No data
No data
-3
No data
0
0
45
7
0*
*NB: Within specified range. Step changes in %RH produce short
term transient response
APPLICATION CIRCUIT
Due to the sensor’s small signal, the amplifier circuit is high-gain;
circuit design and component
choice is therefore critical. Calibration can be achieved either by physically adjusting the gain of
the circuit (manually with a variable resistor or electronically with a digital potentiometer), or us-
ing a fixed circuit gain, known sensor sensitivity and a calibration calculation in software.
The reference circuit above is available pre-built from Dart Sensors for development purposes. It
incorporates a JFET to short the sensor, preventing offsets from building up when not in use. It
also generates a virtual ground, a requirement when operating in single-supply environments.
ELM HOUSE, 54 MARY ARCHES STREET, EXETER, EX4 3BA
TEL: +44 (0)1392 277733
e
-
MAIL: customer.service@dart
-
sensors.com
www.dart
-
sensors.com
CALIBRATION
Production of a suitable span gas for performing formaldehyde calibrations is not trivial, and can
only be achieved through the use of specialist equipment. In limited cases, by arrangement, a
calibration or sensitivity determination can be carried out at the factory for an additional fee.
In production situations the only method approved by Dart Sensors is the use of permeation or
diffusion tube based apparatus with a post-humidification unit. Contact us for advice on the
choice of suitable equipment with which to assemble such an apparatus. Dart Sensors will not
offer technical support where inferior/unsuitable equipment has been used to generate
calibration or test gases.
DIMENSIONS
ORDERING INFORMATION
Part Number
2-FP5
2-FE5
Description
Formaldehyde sensor, 11mm, high catalyst content
Formaldehyde sensor, 11mm
ELM HOUSE, 54 MARY ARCHES STREET, EXETER, EX4 3BA
TEL: +44 (0)1392 277733
e
-
MAIL: customer.service@dart
-
sensors.com
www.dart
-
sensors.com
09032017
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