Testo 6621 Specifications

Humidity transmitter

testo 6621

Highly accurate testo humidity sensor with long-term

stability (±2.0% RH)

Optional 2-line LCD display

P2A software for parameterization, adjustment and analysis,

saves time and costs in commissioning and maintenance

Wall version with
display

Duct version with
display

Optimum calibration concept thanks to adjustment of the

entire signal chain (1-point, 2-point and analog adjustment)

Adjustment without dismantling the transmitter

2 analog outputs (humidity/temperature), option of 1

passive humidity and temperature analog output

A broad variety of the testo 6621 transmitter is available.

Depending on the application in a room or in a duct,

the corresponding designs can be selected. A display

is available as an option. You can choose between

the housing colours grey and white. The testo 6621 is

persuasive in technical terms thanks to the patented

humidity sensors that guarantee the highest accuracy. The

sensors and the analog outputs can be adjusted, analyzed

and parameterized via the external interface using the P2A

software.

%RH

°C

The testo 6621 is a high-performance transmitter for a low

price. It meets the increasing requirements in automated

building services in terms of accuracy, reliability and safety

and thereby saves energy costs.

www.testo.com

testo 6621 – Humidity transmitter

Technical data

testo 6621 –
A01/A03 (wall
version)

testo 6621
– A02 (duct
version)

Parameters

Humidity

Meas. range 0 to 100% RH (>90% RH only briefly)

Accuracy* ±2.0 %RH (0 to 90 %RH),

Temperature
dependency/coefficient

Sensor Testo humidity sensor

Replaceability of sensor Through Testo

Temperature

Meas. range 0 to +60 °C

Accuracy ±0,5 °C / 0,9 °F

Sensor Active signal output: NTC

(not for high humidity processes)

±4 %RH (90 to 100 %RH)

Temperature coefficient: 0.05%/K
(gap of 25 °C/77 °F)

Service

(+32 to +140 °F)

Passive signal output: NI1000

Can be done
by customer (s.
below, Replacement
sensors), subsequent
2-point adjustment
required

-20 to +70 °C
(-4 to +158 °F)

Inputs and outputs

Analog outputs

Number of channels 2 channels (humidity and temperature)

Output type

Measuring rate 1/s

Accuracy of analog
outputs

4 to 20 mA (2-wire)
0 to 1/5/10 V (4-wire)

4 to 20 mA ±0,05 mA
0 to 1 V ±2,5 mV
0 to 5 V ±12,5 mV
0 to 10 V ±25 mV

testo 6621 –
A01/A03 (wall
version)

testo 6621
– A02 (duct
version)

General

Housing

Material / colour ABS/

Dimensions 81 x 81 x 26 mm 81 x 81 x 42 mm

Weight 160 g80 g / 90 g (A03)

Display

Display 2-line LCD (optional)

Resolution Humidity: 0.1 %RH

Operation

Parameterization P2A software

Assembly

Cable screw connection None (cable routed

Other features

Protection class IP30 IP65

EMC According to EC directive 2004/108/EEC

Interfaces 1x mini-DIN for connecting PC

Reaction time t90: < 15 s at 2 m/s;

Scaling range -50 to 100 °C / -58 to 212 °F,

pure white (RAL 9010) or light grey

see drawing for
probe

Temperature: 0.1 °C/°F

1 x M16 x 1,5
through rear wall
opening or
break-out opening on
bottom)

For calibration and adjustment, please note:
The response time may be considerably
higher in static air

0 to 100 %RH

Power

Voltage supply 20 to 30 V AC/DC

Current consumption

Output

2-wire current 4 to
20 mA

4-wire voltage 0 to 10V 24 7

* The determination of the measurement uncertainty takes place

according to GUM (Guide to the Expression of Uncertainty in
Measurement):

In the determination, the accuracy of the measuring instrument
(hysteresis, linearity, reproduceability), the uncertainty contribution of
the test site as well as the uncertainty of the adjustment site/works
calibration are taken into account. For this purpose, k=2 of the extension
factor, the usual value in measurement technology, is used as a basis,
corresponding to a trust level of 95%.

Voltage supply [V] Current consumption

[mA]

20 20

24 20

30 30

30 7

20 20

24 22

30 28

Operating conditions

Electronics temperature
(housing) (with/without
display)

Storage temperature -40 to +70 °C (-40 to +176 °F)

Measuring medium Air in air-conditioning systems or air-

0 to +60 °C/32 to +140 °F (A01/A03),
With display: 0 to +50 °C/+32 to +122 °F;

-20 to +70 °C/-4 to +158 °F (A02),
With display: 0 to +50 °C/+32 to +122 °F

conditioned rooms