Testo 6651, 6681 Operating Manual

testo 6681 · Humidity transmitters

testo 6610 · Probes

P2A software · Parameterizing, adjusting and analyzing

software

Instruction manual en

2

Safety and the environment

Safety and the environment

Avoiding electrical hazards

► Never use the instrument and connected probes to measure on or near

live parts!

► Damaged mains cables must only be replaced by authorized personnel.
► Only have the transmitter wired and connected by authorized personnel

with the voltage disconnected.

► You must always comply with the regulations applicable in your country

to the opening and repair of electrical equipment.

Avoiding personal injury/damage to equipment

► Installation, setting and calibration work must only be carried out by

qualified and authorized personnel!

► Only open the instrument when this is expressly described in the

instruction manual for installation, maintenance or repair purp oses.

► Observe the permissible storage, transport and operating temperatures.
► Never store or operate the product with solvents and do not use any

desiccants.

► Do not use the instrument for control purposes at the same time as

operating or servicing the transmitter.

► Only operate the product properly, for its intended purpose and within the

parameters specified in the technical data. Do not use force.

► Carry out only the maintenance and repair work that is described in the

documentation. Follow the prescribed steps when doing so. Use only
OEM spare parts from Testo.

Any additional work must only be carried out by authorized personnel.
Otherwise Testo will not accept any responsibility for the proper functioning of
the instrument after repair and for the validity of certifications.

Protecting the environment

► Send the product back to Testo at the end of its useful life. We will

ensure that it is disposed of in an environmentally friendly manner.

About this document

About this document

► Please read this documentation through carefully and familiarize yourself

with the product before putting it to use. Keep this document to hand so
that you can refer to it when necessary. Hand this documentation on to
any subsequent users of the product.

► The following conventions are followed in this document:

Character/
display:

Explanation/example

With the signal word Warning!:
Warns against hazards which could result in serious physical

injury if the precautionary measures indicated are not taken,
e.g.:

De-energize the mains connection before connecting the
transmitter!

With the signal word Caution!:

3





Warns against hazards which could result in minor physical
injury or damage to equipment if the precautionary
measures indicated are not taken, e.g.:

Observe the permissible operating temperature!

Important information, e.g.:
Administrator rights are required to install the program under

Windows

®

2000, XP and Vista.

Aim of action, e.g.:

 Assembling the instrument at the process

connection:

Requirement that must be met, e.g.:

 USB drivers are installed.

4

About this document

1

Steps are numbered if a certain sequence of actions must
be followed, e.g.:

1 Loosen and remove housing screws.
2 Remove the upper part of housing.



" to "

Bold type

…>…

[ ]

CAPITAL
LETTERS

A step is not numbered if there are no further steps or if the
step is optional, e.g.:

▪ Insert probe connector into socket of testo 6681 until

it engages.

Example entries are in inverted commas, e.g.:

The value "0" results in ....

Elements of the program interface or instrument display,
e.g.:

The instrument designation appears in the
instrument/parameter file list.

Select Main Menu Channel 1 and confirm with SET.

Functions/paths within a menu, e.g.:
Start > All Programmes > Testo > Transmitter Software.

Buttons which start an action, e.g.:
Confirm the software key with [OK].

Keys on the instrument or keypad, e.g.:
Press ESC.

Contents

Contents

1 TRANSMITTER............................................................................................8

1.1 Specifications...........................................................................................8

1.1.1 Functions and use.......................................................................8

1.1.2 Scope of delivery.........................................................................8

1.1.3 Accessories.................................................................................9

1.1.4 Technical Data............................................................................9

1.1.5 Dimensions ...............................................................................10

1.2 Product description................................................................................11

1.2.1 At a glance................................................................................11

1.2.2 Usable probes...........................................................................12

1.2.3 Display and keypad...................................................................12

1.2.4 Service interface .......................................................................12

1.2.5 Relay board (option)..................................................................13

1.2.6 analog outputs...........................................................................13

1.2.7 Parameters................................................................................13

1.2.8 Scaling ......................................................................................14

1.2.9 Alarm handling..........................................................................17

1.3 Commissioning......................................................................................18

1.3.1 Assembling the instrument........................................................18

1.3.2 Connecting the instrument........................................................21

1.3.3 Adjusting the instrument............................................................33

1.4 Operation...............................................................................................42

1.4.1 Relationship between user menu and mini-DIN socket

is active.....................................................................................42

1.4.2 Key cover ..................................................................................42

1.4.3 Password protection..................................................................44

1.4.4 Structure of user menu..............................................................44

1.4.5 Ov e r v i e w o f t h e t e s t o 6 6 8 1 u s e r m e n u............................................46

1.4.6 The individual main menus .......................................................48

1.5 Status, warning and error messages.....................................................60

1.5.1 Status messages.......................................................................60

1.5.2 Warning messages ...................................................................61

1.5.3 Error messages.........................................................................63

1.5.4 Handling alarm messages ........................................................64

1.5.5 Namur fault conditions ..............................................................66

1.6 Maintenance and cleaning.....................................................................67

1.6.1 Maintaining the instrument........................................................67

1.6.2 Cleaning the instrument............................................................67

5

6

Contents

2 TESTO 6610 PROBES...............................................................................68

2.1 Specifications.........................................................................................68

2.1.1 Functions and use.....................................................................68

2.1.2 Design of the probe...................................................................70

2.1.3 Accessories...............................................................................71

2.2 Product description................................................................................71

2.2.1 Overview of probe and filter types ............................................71

2.2.2 testo 6611 wall probe................................................................76

2.2.3 testo 6612 duct probe...............................................................79

2.2.4 testo 6613 cable probe .............................................................83

2.2.5 testo 6615 trace humidity cable probe (self-adjustment)..........90

testo 6617 cable probe (self-monitoring)...............................................94

2.2.6 testo 6622 duct probe...............................................................98

2.2.7 testo 6623 cable probe ...........................................................101

2.3 Commissioning....................................................................................104

2.3.1 Installing the probe..................................................................104

2.3.2 Connecting/removingthe probe to/from the transmitter ..........108

2.4 Maintenance and cleaning...................................................................109

2.4.1 Replacing filters/protection caps.............................................109

2.4.2 Cleaning the instrument and filter/protection cap ...................112

2.4.3 Replacing the sensor ..............................................................112

3 PARAMETERIZING, AD JUSTING AND ANALYZI NG SOFT WARE

SOFTWARE)..................................................................................113

(P2A

3.1 Specifications.......................................................................................113

3.1.1 Functions and use...................................................................113

3.1.2 System requirements..............................................................114

3.1.3 Scope of delivery ....................................................................114

3.2 First steps............................................................................................115

3.2.1 Installing the software/driver...................................................115

3.2.2 Starting the software...............................................................116

3.3 Using the software...............................................................................117

3.3.1 User interface..........................................................................117

3.3.2 Editing instrument/parameter file............................................119

3.3.3 Analyzing/testing the transmitter.............................................128

3.3.4 Adjusting the transmitter.........................................................134

3.3.5 Transmitter history ..................................................................139

Contents

4 TIPS AND ASSISTANCE............................................................................145

4.1 Questions and answers.......................................................................145

4.2 Accessories and spare parts...............................................................146

4.2.1 Ordering options for testo 6681 transmitter (0555 6681)..................148

4.2.2 Ordering options for testo 6610 probes (0555 6610)......................152

7

8

testo 6681 - 1.1 Specifications

1 Transmitter

1.1 Specifications

1.1.1 Functions and use

The testo 6681 humidity transmitter is used in conjunction with plug-in,
adjusted probes from the testo 6610 range.

Please refer to Chapter 2 testo 6610 probes for information
about commissioning, operating and maintaining the

The testo 6681 humidity transmitter is suitable for the following applications,
for example:

• Process instrumentation

• Clean rooms

• Test benches

• Drying processes

• Production and storage air quality

• Complex room climate applications.

testo 6610 probe.

1.1.2 Scope of delivery

The scope of delivery of the testo 6681 humidity transmitter includes the
following:

• Key cover

• Rear panel bracket

• CD-ROM with catalogue files (PDF) and P2A update (this can onl y be

used in conjunction with the P2A software, which has to be ordered
separately).

testo 6681 - 1.1 Specifications

1.1.3 Accessories

The following accessories are available for the testo 6681 humidity
transmitter:

• Protection caps for probes

• Mains unit

• P2A software (parameterizing, adjusting and analyzing software)

• Assembly accessories.

Information about accessories and their order numbers can
be found in Chapter 4.2 Accessories and spare parts or on
the website at www.testo.com.

1.1.4 Technical Data

9

Parameters

- Humidity (various variables and

units)

- Temperature (°C/°F)

Measuring range

- Depends on probe

Accuracy

- Depends on probe

Resolution

- 0.1 % RH or 0.1 °C/0.1 °F

Meas. cycle

- 1/s

Interface

- Mini-DIN for P2A software

(parameterizing and adjusting
software) and handheld testo
400/650

- optional: Profibus-DP module

Voltage supply

- 2-wire: 12 to 30 V DC

- 4-wire (separate signal and supply

lines):
20 - 30 V AC/DC,
300 mA power consumption

Maximum load

- 2-wire: 100 to 750 Ω

- 4-wire: 500 Ω (power output)

10

testo 6681 - 1.1 Specifications

Analog output

- 4 to 20 mA ± 0.03 mA (2-wire) or

- 0 to 1 V ± 1.5 mV (4-wire) or

- 0 to 5 V ± 7.5 mV (4-wire) or

- 0 to 10 V ± 15 mV (4-wire) or

- 0 to 20 mA ± 0.03 mA (4-wire) or

- 4 to 20 mA ± 0.03 mA (4-wire)

Resolution of analog output

- 12 bit

Relay

- 4 relays, 250 V AC/DC, 3 A

(optional)

Display

- 2-line LCD with plain text line

(optional)

Housing operating temperature

1.1.5 Dimensions

- -40 to 70 °C/-40 to +158 °F, with

display from 0 - 50 °C/+32 to
+122 °F

- With integrated relay: -40 to +60°C

Storage temperature

- - 40 to 80 °C/-40 to +176 °F

Housing, weight

- Metal, 1.960 kg/432 lb

Protection class

- IP 65 only if the transmitter is wired

and/or seal plugs are inserted

Directives, standards and tests

- EC Directive: 2004/108/EC

- EN 61326

Warranty

- Duration: 2 years

- Warranty conditions: See

guarantee card

Dimensions in mm a b

With M 20 cable couplings 144 147
With NPT cable couplings 144 144
With plug-in connections 143

testo 6681 - 1.2 Product description

1.2 Product description

1.2.1 At a glance

1 Keys (only with optional display)
2 Service flap screw connection

(self-locking, 2x)
3 Display (optional)
4 Service flap
5 M 16 x 1.5 screw connection*,

e.g. analog outputs
6 M 16 x 1.5 screw connection*,

e.g. voltage supply
7 Earthing/PE connection
8 M 20 x 1.5 screw connection*,

e.g. relay R 3 and R 4
9 Eyelet for measuring point panel
10 M 20 x 1.5 screw connection*,

e.g. relay R 1 and R 2
11 Probe connector (testo 6610)
12 Upper part of housing
* Alternatively, NPT cable

couplings or M plug-in

connections are available

11

13 Housing screws
14 Socket for probe connector

15 Hole for fastening to rear panel

bracket (M3 x 6 screw)
16 Plastic bracket for assembly on

rear panel

12

testo 6681 - 1.2 Product description

1.2.2 Usable probes

The testo 6681 humidity transmitter can be used with the following probes:

probe Article no. Characteristic

testo 6611 0555 6610-L11 Wall probe version; accuracy to ± 1 % RH;

testo 6612 0555 6610-L12 Duct probe version; accuracy to ± 1 % RH;

testo 6613 0555 6610-L13 Cable probe version; accuracy to ± 1 % RH;

testo 6614 0555 6610-L14 Heated cable probe version; accuracy to

testo 6615 0555 6610-L15 Trace humidity cable probe version;

testo 6617 0555 6610-L17 Cable with cover electrode monitoring probe

testo 6622 0555 6610-L22 Duct probe version; accuracy to ± 1 % RH;

testo 6623 0555 6610-L23 Cable probe version; accuracy to ± 1 % RH;

temperature range -20 °C to +70 °C/-4 to +158 °F

temperature range -30 °C to +150 °C/-22 to +302 °F

temperature range -40 °C to +180 °C/-40 to +356 °F

± 1.0 % RH; temperature range -40 °C to +180 °C/

-40 to +356 °F

accuracy ± 6 K at -60 °Ctd;
temperature range -40 °C to +120 °C/-40 to +248 °F

version; temperature range -40 °C to +180 °C/-40
to +356 °F

temperature range -30 °C to 120 °C/-22 to +248 °F

temperature range -30 °C to +120 °C/-22 to +248 °F

1.2.3 Display and keypad

The display option allows the testo 6681 humidity transmitter to be operated
via the display and four keys.

The LCD display consists of two 7-segment lines for displaying readings and
units and of an information line (for status messages, for example).

The brightness and contrast of the display and the background lighting
(permanent or off) can be changed via the user menu or the P2A software.

1.2.4 Service interface

Behind the service flap is the parameterizing socket (mini-DIN) as an
interface to the P2A software or Testo handheld instrument
(testo 400/testo 650).

testo 6681 - 1.2 Product description

1.2.5 Relay board (option)

This has a floating switch capacity of 250 V AC/3 A. The switching limits and
hysteresis as well as the function as relay for the collective alarm can be set
via the display or the P2A software. Further features include:

• Function of changeover contacts (NC/NO contacts) freely selectable

• 12 terminals for a total of 4 relays.

If no relays are available, settings for monitoring limit values
or alarms can still be controlled via the display. The alarm
status will be shown on the display

Only have the transmitter wired and connected by authorized
personnel with the voltage disconnected.

1.2.6 Analog outputs

For analog outputs, the testo 6681 has either

13

• 2 or optionally 3 current outputs of 4 to 20 mA (2-wire)/0 to 20 mA (4-

wire)/4 to 20 mA (4-wire) or

• 2 or optionally 3 voltage outputs of 0 to 1 V/0 to 5 V/0 to 10 V (4-wire).

The transmitter can be ordered with a third analog output as an option.
In 2-wire operation, channel 1 is used for the supply. The two or optionally

three channels are galvanically isolated in both 2- and 4-wire operation.

Operation with the testo 6614 heated probe, the testo 6615
trace humidity probe, the relay and profibus options or with
the background lighting of the optional display are only
possible in 4-wire operation.

1.2.7 Parameters

The following parameters are displayed:

• Relative humidity in %RH (technical)

• Relative humidity in % WMO* (calculation according to the WMO

standard)

14

testo 6681 - 1.2 Product description

• Temperature °C and °F

• Dewpoint or pressure dewpoint in °Ctd and °Ftd

• Absolute humidity in g/m³ and gr/ft³

• Degree of humidity in g/kg and gr/lb

• Enthalpy in kJ/kg and BTU/lb

• Psychrometer temperature in °Ctw and °Ftw

• Water vapour partial pressure in hPa and "H

• Water content in ppm

• Dewpoint of H

2O2

and % vol

vol

mixture in °Ctm and °Ftm.

* It is possible that condensation appears as of a displayed humidity
starting from 70 % and is shown on the display.

Calculated humidity variables correspond to the medium of
air. With other gases/gas compositions, deviations may
occur, e.g. with the enthalpy

1.2.8 Scaling

There are three types of min./max. values:

O

2

1 The measuring range

The maximum sensor performance is in this range. Values outside of
the measuring range are displayed via messages, for example.
Measuring range, see table (below).

2 Standard scaling

The output signals are assigned to this measuring range as standard:

- during delivery if no entries are made in the order code

- after exchanging the unit, the measuring range recorded in the
instrument is applied as standard.

The transmitter even retains its scaling with the voltage
disconnected.

Measuring range, see table (below).

3 The maximum settings for the manual scaling

- the values are not expressly given in the table. The maximum limits
can be calculated as follows:

testo 6681 - 1.2 Product description

X = difference between MIN. and MAX. value of the standard scaling
(Max. value of standard) + (50 % of X)
(Min. value of standard) - (50 % of X)

- It is thus possible to scale beyond the measuring range, e.g. for the
adjustment of the scaling limits to standard values of a PLC.

Standard

Measuring

range

Physical

Parameter Unit probe

Temperature °C 6611 -20 +70 -20 +70
°F 6611 -4 +158 -4 +158
°C 6612 -30 +150 -30 +150
°F 6612 -22 +302 -22 +302
°C 6613, 6614, 6617 -40 +180 -40 +180
°F 6613, 6614, 6617 -40 +356 -40 +390
°C 6615 -40 +120 -40 +120
°F 6615 -40 +248 -40 +248
°C 6622, 6623 -30 +120 -30 +120
°F 6622, 6623 -22 +248 -22 +248
relative humidity % RH 0 +100 0 +100
WMO relative humidity % RH, 0 +100 0 +100
Dewpoint/pressure dewpoint °Ctd 6611 -80 +70 -80 +100
°Ftd 6611 -112 +158 -112 +212

°Ctd 6615 -60 +30 -80 +100
°Ftd 6615 -148 +212 -112 +212
Mixture dewpoint (H2O2) °Ctm -20 +100 -20 +100
°Ftm -4 +212 -4 +212
Absolute humidity g/m3 all probes 0 600 0 2000
gr/ft3 0 250 0 800
Degree of humidity g/kg all probes 0 13300 0 950 0

°Ctd
°Ftd

6612, 6613, 6614,
6617, 6622, 6623

6612, 6613, 6614,
6617, 6622, 6623

at 1013 hPa
MIN MAX MIN MAX

-20 +100 -80 +100

-112 +212 -112 +212

scaling

MUF

measuring

range

15

16

testo 6681 - 1.2 Product description

Standard

Measuring

range

Physical

Parameter Unit probe

gr/lb 0 93000 0 66500
Enthalpy kJ/kg -40 99999 -40 8000
BTU/lb -18 43000 -18 3500
Psychrometer temperature °Ctw -40 100 -40 180
°Ftw -58 210 -40 356
Water content ppm vol H2O 0 99999 0 99999
% vol 0 100 0 100
Water vapour partial pressure hPa 0 1000 0 7000
inchH2O 0 400 0 2800

at 1013 hPa
MIN MAX MIN MAX

scaling

MUF

measuring

range

testo 6681 - 1.2 Product description

1.2.9 Alarm handling

For upper and lower alarm limits, individual alarms as well as collective
alarms can be specified. If the collective alarm function is activated, an alarm
is triggered as soon as the alarm limit of an alarm is exceeded, if this alarm is
assigned to the collective alarm.

The testo 6681 monitors limit values using relays. If a reading is outside the
limit values, a relay to be specified by the user is switched.

If the reading reverts to more than a specified hysteresis below or above the
limit value, the alarm is cancelled.

In addition, information about the occurrence of error/status messages can
be provided by means of a collective alarm relay, see Chapter 1.5 Status,
warning and error messages.

If multiple alarm messages are activated at the same time,
the last alarm is shown. If the alarm is cancelled again, the
previous messages are no longer shown.

Example:

17

If the condensation of the probe begins, the "Condensation"
message appears on the display and the "Start" status
display. If the condensation is over, the status display
changes from "Start" to "End".

18

testo 6681 - 1.3 Commissioning

1.3 Commissioning

1.3.1 Assembling the instrument

1.3.1.1 Wall mounting
(for testo 6611/6613/6614/6615/6617/6622/6623
probes)

 Attaching rear panel bracket

1

1 Remove locking screw (item (4) of drawing below) and detach rear

panel bracket from plastic bracket (item (2) of drawing below).

2 Hold rear panel bracket in assembly position and mark the three drill

holes.

3 Drill three holes (∅ 5 mm) and insert dowels where necessary.
4 Screw on rear panel bracket.

Remember that the clamping brackets (1)must face the wall.

testo 6681 - 1.3 Commissioning

 Fastening instrument to rear panel bracket

5

1 Slide plastic bracket (2) on the back of instrument onto rear panel

bracket until it engages (see arrows).

2 Insert screw (4) through hole (3) and screw into rear panel bracket.
3 Insert probe connector (5) into socket until it engages.

19

20

testo 6681 - 1.3 Commissioning

1.3.1.2 Duct mounting (for testo 6612 probes)

1 Hold wall/duct bracket (order no. 0554 6651) (6) against duct wall (8)

and mark drill holes for wall/duct bracket and probe shaft.

2 Drill a hole (∅ 12.5 mm) in the duct wall to feed through the probe

shaft.

3 Fasten wall/duct bracket (6) to duct wall with screws (5).
4 Push probe shaft (9) with filter (10) through the middle hole of the

mounting bracket.

The wall/duct bracket (6) has an O-ring (7) to seal it against
the duct. Feed the probe shaft (9) carefully through the
wall/duct bracket so that the O-ring is not damaged.

5 Fix the correct position of the probe shaft (9) with screw (11) and mark

(insert probe shaft as far as possible).

6 Slide plastic bracket (2) on the back of the transmitter onto bracket (3,

4) until it engages.

testo 6681 - 1.3 Commissioning

Take the weight of the transmitter into account. Ensure that
the brackets (4, 6) are fastened securely.

7 Insert screw (1) through the hole on the top of the instrument and

screw into bracket (3).

8 Insert probe connector (12) into socket until it engages.

1.3.2 Connecting the instrument

 Opening the instrument

21

1 Loosen screw connection (1) of service flap and open the flap.

22

testo 6681 - 1.3 Commissioning

2 Loosen and remove housing screws (2).
3 Remove upper part of housing from lower part (3) and place on a

clean surface.

Warning!
Electrical voltage.
Danger of injury!

De-energize the mains connection before connecting the
transmitter!

Only have the transmitter wired and connected by authorized
personnel with the voltage disconnected.

1.3.2.1 Overview of terminals

testo 6681 - 1.3 Commissioning

23

1 Lower part of housing
2 Relay board (option)
3 Relay terminals
4 Insulating trough for relay board
5 Terminal strip for voltage supply

and analog outputs

6 Terminal board

The following description of the terminals refer to this
overview and its numbering.

7 Earthing terminal (internal)
8 M 16 x 1.5 screw connection*
9 Earthing terminal (external)
10 M 20 x 1.5 scr ew connection*
11 Eyelet for measuring point panel
* Alternatively, NPT cable coupling

or M plug-in connection

24

testo 6681 - 1.3 Commissioning

1.3.2.2 Connecting voltage supply and analog outputs

Terminal strip for voltage supply and
analog outputs, item (5) of Overview of
terminals, chapter 1.3.2.1.

1 Feed cable with voltage supply and analog signal lines through opened

M 16 x 1.5 screw connection (item (8) in Overview of terminals,
Chapter 1.3.2.1).

2 Strip the cable ends, clamp wire end ferrules on and screw down onto

voltage terminals.

3 Close M 16 x 1.5 screw connection (item (8) in Overview of terminals,

Chapter 1.3.2.1).

Wiring diagram for 2-wire system (4 - 20 mA)

12 to 30

0 V

2 or 3 channels
4 to 20 mA, max. load 100 to 750 Ω

If the channels have to be galvanically isolated, a separate
mains unit must be used for each channel.

Wiring diagram for 4-wire system
(0 to 20 mA/4 to 20 mA/0 to 1 V/0 to 5 V/0 to 10 V)

CH1

20 to 30
V AC/DC

+

24V

-

+

CH2 CH3

-

+

-

-

+

+

-

0 V

2 or 3 channels
0 to 20 mA/
4 to 20 mA/
max. load per 500 Ω

0 to 1 V/0 to 5 V/0 to 10 V

testo 6681 - 1.3 Commissioning

25

Requirement for the connecting cable of the supply:

• Insulated with cross-section of at least 0.25 sq. mm.

• The supply line must be secured against exceeding 8 A.

• An OFF switch must be installed in an easily accessible

position close by and be marked as such.

1 Feed connection cables of the two, or optionally three, channels

through opened M 16 x 1.5 screw connection (item (8) in Overview of
terminals, chapter 1.3.2.1).

2 Strip the cable ends, clamp wire end ferrules on and screw to channel

terminals as shown in diagram.

3 Close M 16 x 1.5 screw connection (item (8) in Overview of terminals,

Chapter 1.3.2.1).

26

testo 6681 - 1.3 Commissioning

1.3.2.3 Connecting the relay outputs

Only have the transmitter wired and connected by authorized
personnel with the voltage disconnected.

Relay terminal strip, item (3)
of Overview of terminals,
chapter 1.3.2.1

There is the option of twelve terminals for a total of four relays. The
designations NC/C/NO (normally closed contact/root or pin/normally open
contact) are etched on the surface of the board.

Using PG screw connection

1 Feed connection cables for the relays through opened M 20 x 1.5

screw connection (item (10) of Overview of terminals, chapter 1.3.2.1).
2 Strip cable ends and clamp on wire end ferrules.
3 Connect relays according to chosen function (NC/NO) (see diagrams

below; relay 1 is shown as an example of a connection).

Using plug-in connections (optional)

Only insert or disconnect the plug-in connection when the
voltage is disconnected.

4 Clean the connector of the probe line and the coupling of any foreign

matter.

Do not disconnect the connector of the probe line from the
instrument for extended periods to protect against
contamination.

Connection note

testo 6681 - 1.3 Commissioning

27

• For the connection, a double-insulated mains cable
(sheathed cable) with a cross-section of at least 1.5 sq.
mm must be used.

• Cable connection (2) may not be routed in a loop within
the tray (1).

• It is recommended that you always tie 3 cores to one
another using a cable tie (3).

• The insulation of the cable must be fed at least 5 mm (4)
into the tray.

28

(

)

testo 6681 - 1.3 Commissioning

Use of relay as NC contact (NC = normally closed)

Alarm/status light
(example of installation)

250 V AC/DC, 3 A

The busy light (alarm/status light) is permanently on until the
relay opens or the circuit is interrupted. This circuit can
therefore be used to monitor the functionality of the alarm
circuit, as a cable break, for instance, is indicated by the busy
light going off.

Use of relay as NO contact (NO = normally open)

Alarm/status light

example of installation

250 V AC/DC, 3 A

testo 6681 - 1.3 Commissioning

The busy light (alarm/status light) only comes on when the
relay is switched (closed). Monitoring the functionality of the
alarm circuit is therefore not possible with this switching
operation.

5 Close M 20 x 1.5 screw connection (item (10) in Overview of terminals,

Chapter 1.3.2.1).

1.3.2.4 Plug-in connection option

As an option, the PG screw connections of the signal and supply lines can be
replaced with plug-in connections that are installed at the housing, see Fig. 1
and 2. The relay cabling occurs via standard cable entries and PG screw
connections, see Fig. 3 and 4.

Transmitter housing

29

30

testo 6681 - 1.3 Commissioning

Plug-in connections for power supply and channels

M12 plug-in connection (5-pin) socket (1)
View of the plug-in connections in the installed state from outside

Pin Assignment.

1 V 24 ­2 V 24 +
3 + Ch 1
4 - Ch 1
5 PE

M12 plug-in connection (5-pin) connector (2)

Pin Assignment.

1 - Ch 2
2 + Ch 2
3 + Ch 3
4 - Ch 3
5 PE

testo 6681 - 1.3 Commissioning

1.3.2.5 Creating the PE/earthing terminal

As the testo 6681 has a metal housing, we recommend that the instrument
be earthed. This can be done using the earthing terminal within the
instrument (1) or the earthing terminal outside of the instrument (2).

Only use the external earthing terminal in dry interiors.

31

Using the earthing terminal within the instrument

1 Guide PE line (yellow-green) (5) through the cable coupling (x) and fit

cable lug (8). Fix this to the side of the instrument (6) using M 5 screw
(3), washer (4) and snap ring (7) on the internal earthing terminal (1).

2 Place the other cable end on an appropriate (PE) earth conductor, e.g.

an earthing bar.

Using an earthing terminal outside of the instrument

1 Use shielded cable (5) with cable lug (8). Fix this using M 5 screw (3),

washer (4) and snap ring (7) on the external earthing terminal (2).

2 Place the other cable end on an appropriate (PE) earth conductor, e.g.

an earthing bar.

32

testo 6681 - 1.3 Commissioning

1.3.2.6 Closing the instrument

1 Place upper part of instrument on top of lower part (see arrow) and fix

in place with housing screws (1).

2 Close the service flap and tighten screws (2).

testo 6681 - 1.3 Commissioning

1.3.3 Adjusting the instrument

The testo adjusting concept allows the entire signal chain from the sensor
signal (probe) and the digital signal (within the transmitter) through to the
analog signal (transmitter output signal) to be adjusted (see diagram).

1-point adjustment 2-point adjustment Analog adjustment

33

Adjustment via

- testo 400/650 handheld

instrument with
adjustment adapter

- P2A software

- User menu

Adjustment via

- Adjustment keys (1, 2)

- P2A software

Adjustment using a precise
multimeter and
transmission of analog
reference value in

- P2A software or

- User menu

Either the 1-point adjustment or the 2-point adjustment is suitable for
adjusting the sensor signal - digital signal chain.

The testo 6681 transmitter has digital probes whose adjustment information
is stored in the probes' internal memory. Both 1-point and 2-point
adjustments can thus be carried out on another testo 6681 (e.g. in the
calibration laboratory).

34

testo 6681 - 1.3 Commissioning

1.3.3.1 Overview: Adjustment keys and test contacts

1 Status LED
2 Contact ch. 1 +
3 Contact ch. 1 ­4 Adjust key 11.3 %
5 Service interface
6 Adjust key 75,3 %
7 Contact ch. 2 +
8 Contact ch. 2 -

1.3.3.2 1-point adjustment (offset)

In the 1-point adjustment, the reading at the working point is raised to the
reference value so that there is no longer any deviation in the working point.
The reference condition can be measured using a precise handhel d
instrument (e.g. testo 400/650 with precision humidity probe) or be created in
an air conditioning cabinet.

Deviation

WP

Working range

after

before

e.g. scale = 0 - 100 % RH

The advantage of the 1-point adjustment is the good measuring result in the
working range. But the further away the measurement is from the working
point, the greater the deviation can become. The 1-point adjustment should
therefore only be used for a relatively narrow measuring range (working

testo 6681 - 1.3 Commissioning

range), e.g. clean room applications, air conditioning applications for storage
and similar.

The 1-point adjustment can be performed

• via the user menu (see Chapter 1.4.6.9) or

• via the P2A software (see Chapter 3) or

• directly by means of a Testo handheld instrument (testo 400/650) (se e

description of how to proceed below).

Please note that the 1-point adjustment is generally
performed on the basis of the % RH and °C/°F parameters.

 Adjusting testo 6681 using Testo handheld instrument

 The service flap is open, a testo 400/650 handheld instrument with a

precision humidity probe is ready.

5

1

2

3

4

35

1 Connect Testo handheld instrument 400/650 (1) with connected

humidity reference probe (3) (order no. reference set 0699 3656/20) to

36

testo 6681 - 1.3 Commissioning

the service interface (5) of the testo 6681 via the adjustment adapter
(2) (connected to the probe socket 1 of the handheld instrument).

2 Expose the humidity probe (4) of the testo 6681 and the reference

probe (3) to the same reference conditions (e.g. in the humidity
generator) and allow climatic conditions to equalize.

3 Switch on the testo 400/650. The two-part display of the handheld

instrument will show the values of the transmitter on the left, and the
values of the reference probe on the right. The humidity and
temperature values are adjusted to the reference probe using the
Probe > Probe Adjustment menu item on the testo 400/650.

The 1-point adjustment is performed for both the humidity and the
temperature.

4 Disconnect the adapter (2) from the service interface (5).
5 Close the service flap.

1.3.3.3 2-point adjustment

With the 2-point adjustment, the parameter is adjusted to the reference value
at the two standard adjustment points 11.3 % RH and 75.3 % RH. The
reference conditions are created either by using Testo humidity adjustment
set (order no. 0554 0660) or in the humidity generator.

Deviation

after

before

In the 2-point adjustment, the deviations between the reading and the
nominal value are minimized across the entire measuring range. The 2-point
adjustment is therefore recommended for large working ranges, e.g. in drying
processes.

The 2-point adjustment can be performed

• via P2A software (see Chapter 3) or

• using the adjustment keys under the service flap, see description of

how to proceed below.

testo 6681 - 1.3 Commissioning

Adjustment with the standard Testo adjustment salt pots is
not suitable for the testo 6614 (heated for high-humidity
applications) and testo 6615 (trace humidity) probes. The
reference conditions should be generated in a humidity
generator to adjust these probes.

In addition, these probes can also be adjusted at a third
adjustment point by Testo Service.

• testo 6614: third adjustment point at 90 % RH

• testo 6615: third adjustment point at -40 °Ctd/-40 °Ftd

 Adjusting testo 6681 using adjustment keys

37

or

11.3 %
RH

75.3 %
RH

11.3 %
RH

75.3 %
RH

(salt pots) (humidity generator)

38

testo 6681 - 1.3 Commissioning

 The service flap of the testo 6681 is open.

1 Expose the humidity probe of the testo 6681 to the reference condition

of 11.3 % RH for at least 1.5 hours at 25 °C.

2 After this equalization period, press the 11.3 % adjustment key (4) for

at least 10 seconds with something like a ball-point pen that is not too
sharp. The LED (1) flashes when the adjustment process begins. At
the same time, the 2-point adjustment 11.3 % status message
appears on the display

Completion of the adjustment is signalled by the LED (1) coming on
permanently and the Probe reset status message is shown.

Carry out the adjustment analogously for the reference condition

75.3 % RH. Press on the 75.3 % RH adjustment key (6) to do this.

3 Close the service flap.

1.3.3.4 Analog output adjustment

The purpose of adjusting the analog outputs is to adjust the signal chain from
the digital signal (within the transmitter) to the analog outputs. The signal type
that was appointed for the transmitter is adjusted respectively for each
channel (e.g. 4 to 20 mA or 0 to 1 V, etc.).

1 Status LED
2 Contact ch. 1 +
3 Contact ch. 1 ­4 Adjust key 11.3 %
5 Service interface
6 Adjust key 75,3 %
7 Contact ch. 2 +
8 Contact ch. 2 -

testo 6681 - 1.3 Commissioning

 Analog outputs 1 and 2 adjusted

 A precise multimeter (minimum resolution of 6.5 digits, accuracy of

100 mA, e.g. Agilent 34401A) is available.

If only a simple multimeter is available, the analog outputs
may not be adjusted.

 The service flap is open.

1 Connect the inputs of the multimeter with the contacts (2) and (3) for

channel 1 or with contacts (7) and (8) for channel 2.

2 Transfer the reference analog value measured with the multimeter to

the P2A software (see Chapter 3) or enter it via the user menu (see
Chapter 1.4.6.9).

3 Disconnect connections between multimeter and contacts of the

testo 6681 and close service flap.

 Adjusting analog output 3 (optional)

If the optional third analog output is to be adjusted, a cable
connection to measure the analog value must be installed.
Do this by proceeding as follows:

39

1 Open transmitter (see Chapter 1.3.2).
2 Connect measuring cable to the terminals of the third analog output

and guide through the cable coupling and out of the transmitter.

3 Reassemble upper part of transmitter (see Chapter 1.3.2.6).
4 Connect cable ends to the inputs of the multimeter.
5 Transfer the reference analog value measured with the multimeter to

the P2A software (see Chapter 3) or enter it via the user menu (see
Chapter 1.4.6.9).

6 Remove the upper part of the transmitter, detach the cable

connections for the adjustment of the 3rd analog output and
reassemble the transmitter.

40

testo 6681 - 1.3 Commissioning

1.3.3.5 High-humidity adjustment for testo 6614

Mollier diagram

e.g. 73 % RH

"Microclimate"
sensor conditions

After heating

High-humidity process
conditions

Mist

With the testo 6614, the rear of the Testo humidity sensor is heated, creating
a microclimate around the sensor (within the filter) that is constantly 5 K
warmer than the actual process conditions. As can be seen in the Mollier
diagram, this reduces the relative humidity at the sensor from around
100 % RH to a lower value, e.g. 73 % RH. In this range, the reaction time of
the sensor is noticeably shorter than in the condensation range and the risk
of the sensor corroding is also reduced. Using the separate temperature
probe, the testo 6681 transmitter compensates the microclimate conditions
and displays the process readings.

100 % RH

The reference conditions (11.3 % RH and 75.3 % RH) for the
2-point adjustment of the testo 6614 should be generated in a
humidity generator, as humidity adjustment sets cannot be
used due to the heat generated. The adjustment can also be
carried out at a third adjustment point (90 % RH) by Testo
Service so that optimum accuracy is also achieved in the high
humidity ranges.

testo 6681 - 1.3 Commissioning

1.3.3.6 Self adjustment of testo 6615 trace humidity
probe

Conventional trace humidity probes show a steep rise in measuring
uncertainty at low humidities. In the testo 6615 trace humidity probe, these
measuring uncertainties are corrected by means of an automatic self­adjustment process. This means that extremely accurate measuring results
are also attained to -60 °Ctd.

To this end, a temperature sensor is fitted on the back of the testo 6615
which is used as a heater. A humidity and temperature value pair is taken in
both the unheated and heated state. The deviation of the probe obtained
from these pairs of values is automatically corrected.

testo 6615:

testo 6615:

probe

Fühler-

behaviour

verhalten

"Duration of heating phase"

Parameter

parameter

„Dauer Heizphase“

"Self-adjustment cycle time"

„Zykluszeit Selbstabgleich“

41

Analog

Analog-

output °Ctd/

Ausgang

°Ftd

°Ctpd/
°Ftpd

Heizphase

Heating phase

Heating phase

Heizphase

The heating time and storing of cycles can be edited in the P2A software; for
example, they can be deactivated by setting the two parameters to "0".

42

testo 6681 - 1.4 Operation

Important:

• Deactivating the adjustment function of the testo 6615

will reduce measuring accuracy and should therefore
be restricted to the shortest possible length of time.

• During the heating phase, the relay and analog

outputs, the display value and output value are
"frozen", see diagram above. Self-adjustment active
is shown in the display until it has finished. The factory
setting for the heating phase is 15 minutes per day.

• In the factory setting, a third adjustment point (-

40 °Ctd) is approached for the testo 6615 in addition to
the 2-point adjustment.

This special adjustment can be performed again by
your Testo Service team if necessary.

1.4 Operation

1.4.1 Relationship between user menu and
mini-DIN socket is active

The testo 6681 can be parameterized using either the user menu or the P2A
software (see Chapter 3).

The testo 6681 humidity transmitter can only be operated via
the display and keypad if the display option is available.

If the testo 6681 is connected to the P2A software, the user
menu is blocked for the duration of the communication. The
message Service plug is shown in the display of the
testo 6681. As soon as the P2A software is disconnected, the
user menu is accessible again.

1.4.2 Key cover

To prevent unauthorized operation of the keys, the standard key frame can
be replaced with a key cover (see below).

testo 6681 - 1.4 Operation

If the key cover has been assembled, the service flap must be opened for
operation, see Section Opening the instrument, Chapter 1.3.2.

 Attaching the key cover

43

 The service flap is open, see Opening the instrument, Chapter 1.3.2.

1 Undo screws (3) and remove key frame (2).
2 Insert key cover (1) into service flap and tighten screws (3).
3 Close and screw down the service flap.

44

testo 6681 - 1.4 Operation

1.4.3 Password protection

The user menu can be protected with a four-digit numerical code (see Editing
Main Menu Settings, Chapter 1.4.6.5) so that access to the user menu is
denied to unauthorized persons not familiar with this numerical code.

If the password protection is not to be used, the numerical code "0000" must
be entered. This is also the status upon delivery.

1.4.4 Structure of user menu

At the main menu level, the user menu comprises the following:

• Main menu of channel 1

• Main menu of channel 2

• Main menu of channel 3 (if this option is available)

• Main Menu Alarm

• Editing Settings main menu

• Analysis main menu

• Main Menu Messages

• Ident main menu

• Adjustment main menu

• Reset main menu

19.3 °C

57.8 % RH

-4.1 °Ctd

Channel 1 display

Channel 2 display

Channel 3 display or for messages

testo 6681 - 1.4 Operation

Four keys enable the user to navigate/scroll through the menus and
enter/amend values and settings:

Key Function/description

SET

ESC

X

S

- In Measuring Mode: changes to parameterization

- In Parameterizing Mode: confirms a selection or setting

- Leaves a menu (without modifying any settings)

- Selecting: scrolls through menus (downwards) or selectable

alternatives

- Editing: changes to next digit (to the right)

- Selecting: scrolls through menus (upwards) or selectable alternatives

- Editing: increases the value of the current digit by 1

45

46

testo 6681 - 1.4 Operation

1.4.5 Overview of the testo 6681 user menu

testo 6681 - 1.4 Operation

47

48

testo 6681 - 1.4 Operation

1.4.6 The individual main menus

1.4.6.1 Editing Main Menu Channel 1

An overview is given in Overview of the testo 6681 user menu, Chapter 1.4.5.
You can perform basic settings for channel 1.

1 In Measuring Mode, press SET, select Main Menu Channel 1 using X

or S and confirm selection with SET.

One of the following parameters can now be selected using X or S, after
which the selection must be confirmed with SET:

• Channel 1 unit

The parameter for this channel is selected.
Selection: % RH, °C, °F, °Ctd, °Ftd, g/m³, gr/ft³, g/kg, gr/lb, kJ/kg,
BTU/lb, °Ctw, °Ftw, "H2O, hPa, ppm

Edit/select parameter with X or S, confirm with SET or abort input
with ESC.

• Scale minimum for channel 1

The lower scale limit is edited;
Unit as selected above (example: 4 mA = 0 % RH).

Editing the value: Scroll one digit to the right using X, increase value
of digit by 1 using S. Confirm with SET or abort entry with ESC.

• Scale maximum for channel 1

The upper scale limit is edited;
Unit as selected above (example: 20 mA = 100 % RH).

Editing the value: Scroll one digit to the right using X, increase value
of digit by 1 using S. Confirm with SET or abort entry with ESC.

• Signal delay ("Damping") for channel 1

The analog signal can be delayed("Damping"); a time constant is
selected for this (1 = no delay; 15 = longest delay).
Edit/select parameter using X or S, confirm with SET or cancel entry
via ESC.

2 Continue to Main Menu Channel 2 using X or S or return to

Measuring Mode by pressing ESC.

, % Vol, °Ctm, °Ftm.

vol

1.4.6.2 Editing main menu of channel 2

See channel 1.

1.4.6.3 Editing main menu of channel 3 (if this option is

available)

See channel 1.

testo 6681 - 1.4 Operation

1.4.6.4 Editing Main Menu Alarm

With the alarm, the relays, available as options, are programmed. In addition,
the alarm statuses are shown on the display (top right) (even without
relays).You can choose whether the alarm is to be used to monitor limit
values or as a collective alarm. If an alarm is to be used to monitor limit
values, you can choose between monitoring the minimum or maximum value
and set a limit value and hysteresis for each alarm.

1 In Measuring Mode, press SET, select Main Menu Alarm using X or

S and confirm selection with SET.

Four alarms can be parameterized.

2 Select Alarm x using X or S and confirm selection with SET.

 Using alarm to monitor limit values

Monitoring minimum Monitoring maximum

Hysteresis Hysteresis

On On

NO contact

Off Off

49

On On

Off

Limit value Limit value

NC contact

Off

Cannel 2
e.g. °C

3 Select Channel x (e.g. "Channel 1") using X or S and confirm

selection with SET.

4 Select Max control or Min control with X or S (see graphic).
5 Press SET and edit limit value and hysteresis: Scroll one digit to the

right using X, increase value of digit by 1 using S. Confirm with SET
or abort entry with ESC.

6 Return to Channel x by pressing ESC.
7 Return to Alarm x by pressing ESC.
8 Change to the other relays using X or S and perform settings in the

same way.

50

testo 6681 - 1.4 Operation

 Using alarm as collective alarm or not using it at all

If the collective alarm is assigned to an alarm, the relay is switched as soon
as (at least) one of the warning or error messages of the testo 6681
transmitter (or the connected testo 6610 probe) is activated.

Note:
The messages affecting the collective alarm can only be

selected in the P2A software, see Chapter 3.

 Alarm is selected (see previous steps 1 and 2).

1 Specify with X or S whether Alarm x is to be used as the Alarm

relay or is not to be used. Confirm selection with SET and return to
Alarm x.

2 Change to another alarm using X or S and perform settings in the

same way.

3 Continue to Main Menu Settings using X or S or return to Measuring

Mode by pressing ESC.

1.4.6.5 Editing Main Menu Settings

You can edit instrument settings and other settings.

▪ In Measuring Mode, press SET, select Main Menu Settings usi ng X

or S and confirm selection with SET.
You can edit settings for:

• Display

• Language

• H

• Absolute pressure unit

• Absolute pressure

• Code

proportion by weight entry (optional with 3rd analog output)

2O2

Unit: %

Selection: bar, psi, mPa, hPa

Unit as selected above.

 Editing display settings

You can set the brightness and contrast of the display.

1 Select Display Settings using X or S and confirm selection with

SET.

testo 6681 - 1.4 Operation

2 Select Backlight or Contrast using X or S and confirm selection with

SET.

One of the following parameters can now be selected using X or S, after
which the selection must be confirmed with SET:

• Backlight

The display illumination is changed.
Edit/select parameter with X or S, confirm with SET or abort input

with ESC (the effect of the change in parameter can be seen during
input).

• Contrast

The brightness difference between the display background and the
displayed values is changed.

Edit/select parameter with X or S, confirm with SET or abort input
with ESC (the effect of the change in parameter can be seen during
input).

• Backlight on 24 h

Using X or S select On or Off and confirm with SET.
Off: The display light switches off automatically if no button was

pressed for 10 seconds.

On: The display light is activated

3 Go back to Display Settings by pressing ESC and continue to

Language using X or S.

51

 Selecting language

You can select the language for the plain text line in the display.

▪ Press SET, select required langua ge with X or S, confirm selection

with SET and return to Language.

Only choose a language that you can understand well.

 Editing H

This menu is only used to parameterize humidity measurements in H
atmospheres (e.g. in sterilization processes) and determines whether °Ctm
or °Ftm is the output parameter.

1 Select H

with SET.

proportion by weight (optional with 3rd analog output)

2O2

Weight Proportion using X or S and confirm selection

2O2

2O2

52

testo 6681 - 1.4 Operation

The selection H2O2 Water or H2O2 Vapour in the submenu describes
whether H

2O2

in the process.

is created through evaporation or is actively evaporated

2 Select H

Water or H2O2Vapour using X or S and confirm with

2O2

SET.

3 Editing proportion by weight of H

in % (% H2O2 proportion by

2O2

weight in the liquid end solution): Scroll one digit to the right using X,
increase value of digit by 1 using S. Confirm with SET or abort entry
with ESC.

4 Go back to H

by pressing ESC and continue to Absolute pressure

2O2

unit using X or S.

 Selecting absolute pressure unit (Abs. pressure unit)

This parameter determines the humidity variables, atmospheric dewpoint
(°CtA, °FtA), relative humidity (g/kg or gr/lb) and water content (ppm

or %

vol

vol).

1 Press SET, select desired unit (selection: bar, psi, mPa, hPa) using X

or S confirm selection with SET or cancel with ESC.

2 Continue to Absolute Pressure with X or S.

 Editing absolute pressure(Abs. pressure value)

You can set a value for the process absolute pressure.

1 Using X or S, select Abs. pressure value and confirm selection with

SET.
The absolute pressure is displayed.

2 Scroll one digit to the right using X, increase value of digit by 1 using

S. Confirm with SET or abort entry with ESC.

3 Press SET and return to Abs. pressure value
4 Return to Main Menu Settings by pressing ESC.
5 Continue to Main Menu Analysis using X or S or return to Measuring

Mode by pressing ESC.

 Editing code settings

You can set the access code (password).

testo 6681 - 1.4 Operation

If a code other than "0000" (factory setting) is set, the
transmitter can only be operated once this code has been
entered via the menu.

1 Select Code using X or S and confirm selection with SET.
2 Scroll one digit to the right using X, increase value of digit by 1 using

S. Confirm with SET or abort entry with ESC.

3 Return to Code by pressing ESC.

1.4.6.6 Editing Analysis main menu

You can test the functionality of analog and relay outputs. In addition, you
can read off the minimum and maximum readings (since the last voltage
supply or reset of the min./max. values

 Testing functionality of analog outputs

This function affects the analog outputs directly, not only the
test contacts.

1 In Measuring Mode, press SET, select Main Menu Analysis using X

or S and confirm selection with SET.
Test Analog Output is shown.

).

53

2 Press SET, choose between Analog Output 1, 2, 3 with X or S.
3 Press SET, scroll one digit to the right using X, increase value of digit

by 1 using S. Any analog output value can be predefined, e.g. for an
analog output of 4 to 20 mA, the value "6.0 mA". Confirm with SET or
abort entry with ESC.

4 Accept setting by pressing SET and test with multimeter (minimum

requirement: resolution of 6.5 digits, accuracy of 100 nA):
Analog output 1 or 2: via test contacts under service flap, see diagram.

54

testo 6681 - 1.4 Operation

1 Channel 1 test

contacts
2 Service interface
3 Channel 2 test

contacts
4 Ends of channel 3

cables
5 Multimeter

Analog output 3: Connect measuring cables to terminals for channel 3,
guide measuring cables out of housing and perform measurement
outside of the transmitter, see diagram.

5 Return to Test Analog Output using ESC and continue to Test Relay

Output using X or S.

 Testing functionality of relay outputs

1 Press SET, choose between Alarm 1, 2, 3, 4 with X or S.
2 Press SET.

The relay can now be tested. You can choose between OFF and ON
using X or S. If ON is chosen, the NO contact is closed, the NC
contact opened. If OFF is chosen, the NC contact is closed, the NO
contact opened.

3 To test, route a measuring cable from the relay terminals (see

Chapter 1.3.2.3) out of the transmitter to a multimeter (resistance
measurement) or continuity tester.

4 Go back to Test Relay Output by pressing either SET (starts relay

test) or ESC (exits the menu without relay test).

 Reading off min./max. values of channels

To reset the max./min. values, see Chapter 1.4.6.10 Editing
Reset main menu

1 Read off the min./max. values of the three channels by pressing X or

S one after the other and return to Main Menu Analysis using ESC.

2 Continue to Main Menu Message using X or S or return to

Measuring Mode by pressing ESC.

testo 6681 - 1.4 Operation

1.4.6.7 Editing Message main menu

Messages can be confirmed/acknowledged, the last messages can be called
up and the display of the messages can be switched on or off.

Operating hours at the time of
message

Message number/number of messages
present
Example: "4/7" refers to the fourth of
seven messages

Message text

348

4/7

Scaling changed

Using the P2A software (see Chapter 3) you can predefine
which of the messages are to be shown in the display.

h

55

1 In Measuring Mode, press SET, select Main Menu Message using X

or S and confirm selection with SET.

2 Confirm Confirm message using SET.
3 Select Last messages using X or S and confirm with SET.
4 Scroll between the messages recorded so far using X or S and press

ESC to return to Last messages.

5 Continue to Display of message with X or S.

ON: Measurements are shown on the display in Measuring Mode.
OFF: No messages shown on display.

6 Select ON or OFF using X or S and confirm selection with SET.
7 Return to Main Menu Message by pressing ESC.
8 Continue to Main Menu Ident using X or S or return to Measuring

Mode by pressing ESC.

An overview of the messages can be found in
Chapter 1.5 Status, warning and error messages.

56

testo 6681 - 1.4 Operation

1.4.6.8 Calling up Main Menu Ident

6681

Instruments or probe type

2.01

Serial

The serial numbers of the transmitter and probe can be read off.

1 In Measuring Mode, press SET, select Main Menu Ident using X or S

and confirm selection with SET.
The type, firmware version and serial number of the transmitter are

displayed.

2 Press ESC to return to the Main Menu Ident or read off the type,

firmware version and serial number of the probe using X or S and
then press X or S to return to the Main Menu Ident.

3 Continue to Main Menu Adjust using X or S or return to Measuring

Mode by pressing ESC.

Firmware version
Serial number

1.4.6.9 Editing Adjust main menu

A reference value can be entered for both relative humidity (RH) and
temperature (°C/°F) for the 1-point adjustment. Please refer to the description
in Chapter 1.3.3.2.

In addition, the analog outputs can be adjusted. See Chapter 1.3.3.4 for
instructions on how to do this.

The 2-point adjustment cannot be performed via the user
menu. This is done using the adjustment buttons or P2A
software, see Chapter 1.3.3.3 or Chapter 3.

testo 6681 - 1.4 Operation

 Enter reference value for 1-point adjustment

Please also refer to Chapter 1.3.3.2.

1 In Measuring Mode, press SET, select Main Menu Adjust using X or

S and confirm selection with SET.

Reference value % RH is displayed.

2 Press SET, edit value: Scroll one digit to the right using X, increase

value of digit by 1 using S. Confirm with SET or cancel entry with
ESC.

3 Continue to Reference value temp with X or S.
4 Press SET and Reference value °C is displayed.
5 Press SET, edit value: Scroll one digit to the right using X, increase

value of digit by 1 using S. Confirm with SET or abort entry with ESC.

6 Continue to Reference value °F with X or S.
7 Press SET, edit value: Scroll one digit to the right using X, increase

value of digit by 1 using S. Confirm with SET or abort entry with ESC.

8 Continue to Analog Adj. Ch. 1 with X or S.
9 Continue with the adjustment of the analog outputs (see below, step 2)

or press ESC to return to Main Menu Adjustment.

10 Continue to Main Menu Reset using X or S or return to Measuring

Mode by pressing ESC.

57

 Performing analog adjustment

Please refer to Chapter 1.3.3.4.

1 In Measuring Mode, press SET, select Main Menu Adjust using X or

S and confirm selection with SET.

Each channel is adjusted at three points in the analog range
(at 10 %; 50 %; 90°% of the analog scale).

2 Select Analog Adj. Ch. 1 using X or S and confirm with SET.
3 Select Adj. Point 1 using X or S.

58

testo 6681 - 1.4 Operation

4 Press SET. Read off multimeter display (e.g. 5.601 mA) and enter this

value in the user menu. Do this by scrolling one digit to the right using
X and increasing the value of digit by 1 using S. Confirm with SET or
abort entry with ESC.

5 Select Adj. Point 2 using X or S.
6 Press SET. Read off multimeter display (e.g. 12,001 mA) and enter

this value in the user menu. Do this by scrolling one digit to the right
using X and increasing the value of digit by 1 using S. Confirm with
SET or abort entry with ESC.

7 Select Adj. Point 3 using X or S.
8 Press SET. Read off multimeter display (e.g. 18,401 mA) and enter

this value in the user menu. Do this by scrolling one digit to the right
using X and increasing the value of digit by 1 using S. Confirm with
SET or abort entry with ESC.

9 Continue to Analog Adj. Ch. 2 or 3 with X or S (repeat steps 3 to 8).
10 Return to Main Menu Adjust by pressing ESC.
11 Continue to Main Menu Reset using X or S or return to Measuring

Mode by pressing ESC.

testo 6681 - 1.4 Operation

1.4.6.10 Editing Reset main menu

You can reset the factory settings for the following:

• Instrument

• Sensor/probe

• Min./max. values

Resetting to the factory settings means resetting to the order
specification, i.e. the specific condition at the time of supply to

1 In Measuring Mode, press SET, select Main Menu Reset using X or

S and confirm selection with SET.

Reset device to factory settings is displayed.

2 Select the setting to be reset using X or S and confirm selection with

SET.

Reset Completed is displayed.

3 Press ESC or SET to return to reset setting and press ESC to return to

Main Menu Reset.

4 Continue to Main Menu Channel 1 using X or S or return to

Measuring Mode by pressing ESC.

the customer.

59

60

testo 6681 - 1.5 Status, warning and error messages

1.5 Status, warning and error
messages

To achieve optimum operational reliability (machine
availability), the transmitter provides the following via the user
menu (see Chapter 1.4) or the P2A software (see Chapter 3):

• Status messages,

• Warning messages and

• Error messages

for either the testo 6681 or the connected testo 661x probe
as applicable.

All messages are stored in the transmitter with an operating
hours stamp. Use the user menu (see Chapter 1.4.6.7) or
P2A software (see Chapter 3) to view the message history.

In the transmitter, the last 180 messages are stored in a ring
memory, but there is no restriction in the P2A software.

1.5.1 Status messages

Status messages show the current operating mode of the testo 6681.

Message Display Description

00300 New limit value The limit value has been changed or shifted
00301 Scaling changed The scaling has been changed
00500 Transmitter reset: The transmitter is reset to the factory settings

and is restarted.
0052F Reset Min/Max Resets all saved Min/Max values for all channels
02506 Probe co nnection A probe has been connected
01D19 Service plug The Mini-DIN socket is connected to: the USB

00307 User Setting Change User Setting Change: General settings were

02d07 Probe d isconnected No probe is connected

adapter for P2A software, the adjustment

adapter or the service plug (is not recorded/no

number)

changed for the transmitter.

testo 6681 - 1.5 Status, warning and error messages

Message Display Description

02104 Analog out adjust An analog adjustment has been made
02101 1-point adjustment A 1-point adjustment is performed.
02102 2-point adjustment

11,3%

02103 2-point adjustment

75.3%

02105 Self-ad justment active For testo 6615 probe only: The probe performs

02518 Probe reset Probe reset: The probe performs a reset

As part of the 2-point adjustment, an adjustment
is performed at 11.3 % RH

As part of the 2-point adjustment, an adjustment
is performed at 75.3 % RH

an automatic self-adjustment

1.5.2 Warning messages

Warning messages show an early warning or a current malfunction which
may negatively impact measuring.

Message Display Cause Remedying of fault

02101 2-point adjustment

drift*

00E00 T ambient high** The ambient temperature

00E01 T ambient low** The ambient temperature is

00E02 Supply voltage

low**

In the 2-point adjustment,
corrections repeatedly
occur in the same direction;
this may indicate a sensor
drift

exceeds the permissible
temperature for the
transmitter

below the permissible
temperature for the
transmitter

The supply voltage is below
the minimum voltage
required for the transmitter

Send the probe into Testo
Service

Take necessary
measures to lower
ambient temperature, e.g.
through venting or cooling

Take necessary
measures to raise
ambient temperature, e.g.
through heating

Ensure sufficient voltage
supply

61

62

testo 6681 - 1.5 Status, warning and error messages

Message Display Cause Remedying of fault

00E00 T process high** The process temperature

exceeds the temperature
designated for the probe

Remove the probe from
the process and take any
necessary measures to
lower the process
temperature

02806 Condensation* 100 % RH has been

reached, condensation

Take measures to reduce
process humidity

developing

02807 Valu es less than

0 % RH**

The adjustment or sensor
is faulty

Check adjustment (via
P2A adjustment history,
perform 2-point
adjustment where
necessary)

If the problem persists,
contact Testo Service

02809 Sensor early

warning*

For testo 6617 probe only:
The cover electrode of the
sensor is damaged; this
may soon cause the sensor
to break

Carry out visual
inspection

If the mirror-like surface of
the sensor is dirty or
damaged, contact Testo
Service

* Early warning
** Current malfunction

testo 6681 - 1.5 Status, warning and error messages

1.5.3 Error messages

Error messages show a current malfunction.

Message Display Cause Remedying of fault

03401 No probe signal The probe communication

03508 Wrong probe The connected probe is not

01528 Watchdog error Due to a processor error,

0300A % RH sensor

short-circuit

0300B %RH sensor

broken

0300C T sensor short-

circuit

0300D T sensor broken The temperature sensor is

03105 Self-adjustment

error

is interrupted

compatible with the present
transmitter

the transmitter performs an
automatic restart

Short-circuit in humidity
sensor

The humidity sensor is
damaged (sensor broken)

Short-circuit in temperature
sensor

damaged (sensor broken)
For testo 6615 probe only:

The automatic self­adjustment was faulty

Ensure that the probe
connector is fully
engaged in the
transmitter.

If communication still
cannot be established,
contact Testo Service

Use a compatible probe
Note: The 660x probes

match the 665x
transmitter, and the 661x
probes the 668x
transmitter

If the problem occurs
frequently, contact Testo
Service

Contact Testo Service

Contact Testo Service

Contact Testo Service

Contact Testo Service

Contact Testo Service

63

64

testo 6681 - 1.5 Status, warning and error messages

1.5.4 Handling alarm messages

Shown on the

display 1

Can be used for

collective alarm

Additional

2

Message
start/end

New limit value x x
Scaling changed x x
Transmitter reset x x
Reset Min/Max x
Transmitter refresh x
Probe connection
Service plug
User Setting Change x
Probe disconnected
Analog out adjust x x
1-point adjustment x x
2-point adjustment 11,3% x x
2-point adjustment 75.3% x x
Probe self-adjustment x x
Probe reset x x
2-point adjustment drift* x
T ambient high** x
T ambient low** x
Supply voltage low** x
T process high** x
Condensation* x
Values less than

x

0 % RH**
Sensor early warning* x
No probe signal x
Wrong probe
Watchdog error x

testo 6681 - 1.5 Status, warning and error messages

Shown on the

display 1

% RH short-circuit x
%RH sensor broken x
T short-circuit x
T sensor broken x
Self-adjustment error

Can be used for

collective alarm

Additional

2

Message
start/end

*

If multiple messages/alarms are activate d at the same time, only the last

message/alarm is shown. If this is cancelled, the other messages that are
still active are no longer displayed.

**

The message can be assigned the collective alarm function, which means

that the collective alarm is activated as soon as at least one of the
messages assigned to it is activated. The collective alarm can be assigned
to each of the 4 optional relays. The collective alarm is then always the
same, as it can only be defined once.

Execute Confirm message function (via control keys at transmitter):

65

• The message/alarm is no longer shown on the display. If multiple
messages/alarms are active at the same time, all are reset
simultaneously.

• If at least one message is assigned to the collective alarm, the collective
alarm is reset. If the collective alarm is set on a relay, the relay is also
reset, meaning switched to its neutral position.

66

testo 6681 - 1.5 Status, warning and error messages

1.5.5 Namur fault conditions

If the faults named in the following table occur, the analog outputs output
special values that enable a general fault warning in the higher-level control
system. The values correspond to the "Namur" industry standard.

Display message Class 0-20mA 4-20mA 1V 5V 10V

No communication Error 21mA 21mA 1.2V 5.5V 11V
No probe signal Error 21mA 21mA 1.2V 5.5V 11V
Wrong probe Error 21mA 21mA 1.2V 5.5V 11V
Watchdog error Error 21mA 21mA 1.2V 5.5V 11V
Values < 0 % RH Underrange 0mA 3.8mA 0V 0V 0V
Condensation Overrange 20.5mA 20.5mA 1.2V 5.5V 11V
%RH short-circuit Error 21mA 21mA 1.2V 5.5V 11V
%RH sensor broken Error 21mA 21mA 1.2V 5.5V 11V
T short-circuit Error 21mA 21mA 1.2V 5.5V 11V
T sensor broken Error 21mA 21mA 1.2V 5.5V 11V
Probe disconnected Error 21mA 21mA 1.2V 5.5V 11V
Reading < min. scale Underrange 0mA 3.8mA 0V 0V 0V
Reading > max.

scale

Overrange 20.5mA 20.5mA 1.2V 5.5V 11V

Analog output

testo 6681 - 1.6 Maintenance and cleaning

1.6 Maintenance and cleaning

1.6.1 Maintaining the instrument

We recommend that the adjustment and settings of the transmitter be
checked at regular intervals using the

• User menu (Chapter 1.4) or

• P2A software (Chapter 3)

Convenient "remote monitoring" of the transmitter can be implemented, for
example by using a relay as a collective alarm (see Chapter 1.4.6.4) whose
messages are forwarded to a local alarm transmitter (horn, light) or PLC.

1.6.2 Cleaning the instrument

▪ Only clean the instrument carefully with a moist cloth.
▪ Do not use aggressive cleaning agents.
▪ Do not use any solvents.
▪ Do not touch or damage the sen sor.

67

68

testo 6610 - 2.1 Specifications

2 testo 6610 probes

2.1 Specifications

2.1.1 Functions and use

The plug-in, adjusted probes from the testo 6610 range are used in
conjunction with the testo 6681 humidity transmitter.

These measuring units are suitable for the following applications, for
example:

• Process instrumentation

• Clean rooms

• Test benches

• Drying processes

• Production and storage air quality

• Complex room climate applications.

2.1.1.1 Digital probes:

The probes are adjusted in the factory and transmit their adjustment data to
the internal memory of the testo 6681 transmitter. The information is
transmitted between the probe and transmitter in a purely digital form. The
probes can therefore be disconnected from the transmitter for adjustment or
servicing while the transmitter itself can remain at the measuring point.

Hint:

The transmitter identifies the probe and records that a probe was connected
in the history.

We recommend in this case that a probe of the same type be
inserted into the transmitter immediately in order to be able to
continue measuring with minimal interruption.

The testo 6681 transmitter cannot be run with the testo 6600
probes; testo 6610 probes must be used.

testo 6610 - 2.1 Specifications

2.1.1.2 The Testo humidity sensor

With the Testo humidity sensor, which has been in successful use and
continually improved for more than ten years, the focus has from the very
beginning been on both accuracy parameters, namely measuring uncertainty
and long-term stability.

The capacitive humidity sensor is in principle a plate capacitor consisting of
two electrically conductive plates (electrodes (1) and (2), see diagram below)
opposite each other.

A humidity-sensitive polymer (5) serves as the dielectric. The special feature
lies in the perfect way the individual layers are matched to each other. This is
evident particularly in the top electrode, which has to perform two tasks that,
at first glance, appear contradictory: it must be completely permeable to the
water vapour that is to be fed into the polymer dielectric, but at the same time
it must be impervious, smooth and repellent to condensate, oil and dirt in
order to protect the sensor.

1 Cover electrode
2 Bottom electrode
3 Substrate

(Ceramic substrate for
mechanical protection)

4 Connections

(protected against corrosion)

5 Dielectric layer

69

The humidity sensor cannot be exchanged by the customer.
The humidity sensor may not be damaged or touched.
Contamination and damage lead to an impairment of the
measurement and the measuring accuracy.

2.1.1.3 Self-diagnosis

The probes in the testo 6610 range monitor their functionality themselves and
report the following faults:

• Sensor breaks

• Sensor short-circuit

70

testo 6610 - 2.1 Specifications

• Condensation

The condensation message is issued at a reading of 100 % RH and
deactivated once the readings are within the valid range.

• Error message with drift at the adjustment points

• Value for relative humidity less than 0 % RH.

The trigger threshold is set at -2 % RH. This means that an error
message is only issued once a clear effect is discernible.

• Early warning when sensor corrosion is starting to develop

The testo 6617 probe is able to signal the first signs of corrosion. The
probe can thus be changed at an early stage without interrupting the
machine availability.

• Self-adjustment (testo 6615 only)

• Excess temperature

Error message if permissible process temperature is exceeded

2.1.2 Design of the probe

The probes of the testo 6610 range are made up of the following components
(included in delivery):

• Probe connector

• Probe shaft with protection cap and sensors (% RH and °C or °F)

• Mounting bracket (for testo 6612 duct version)

• Probe cable (testo 6612 to 6617, 6622, 6623 duct and cable version),

bend radius minimum

Ø 50 mm

Probe connector

testo 6610 - 2.2 Accessories

Probe cable Probe

71

Protection cap, sensor

probe

2.2 Accessories

The following accessories are available for probes in the testo 6610 range:

• Filters and protection caps (see Chapter 2.3.1.4 Filters)

• Calibration certificates according to ISO and DKD (see Cha pter 4.2

Accessories and spare parts).

2.3 Product description

2.3.1 Overview of probe and filter types

2.3.1.1 Probe version

A detailed description of the probe versions can be found
from Chapter 2.3.2 onwards.

The following probe versions are available for the testo 6681 humidity
transmitter:

Version Article no. Characteristic

testo 6611 0555 6610-L11 Wall probe version; accuracy to ± 1 % RH;

temperature range -20 °C to +70 °C/-4 to +158 °F

testo 6612 0555 6610-L12 Duct probe version; accuracy to ± 1 % RH;

temperature range -30 °C to +150 °C/-22 to +302 °F

testo 6613 0555 6610-L13 Cable probe version; accuracy to ± 1 % RH;

temperature range -40 °C to +180 °C/-40 to +356 °F

72

testo 6610 - 2.3 Product description

Version Article no. Characteristic

testo 6614 0555 6610-L14 Heated cable probe version; accuracy to ± 1 % RH;

temperature range -40 °C to +180 °C/

-40 to +356 °F

testo 6615 0555 6610-L15 Trace humidity cable probe version;

accuracy ± 6 K at -60 °Ctd; temperature range -40
°C to +120 °C/-40 to +248 °F

testo 6617 0555 6610-L17 Cable with cover electrode monitoring probe

version; accuracy ± 1.2 % RH; temperature range ­40 °C to +180 °C/-40 to +356 °F

testo 6622 0555 6610-L22 Duct probe version; accuracy to ± 1 % RH;

temperature range -30 °C to +120 °C/-22 to +248 °F

testo 6623 0555 6610-L23 Cable probe version; accuracy to ± 1 % RH;

temperature range -30 °C to +120 °C/-22 to +248 °F

2.3.1.2 Determining the accuracy/measuring uncertainty

The entries for the measuring uncertainty for the probe are determined in
accordance with GUM (Guide to the Expression of Uncertainty in
Measurement/DIN V ENV 13005). All parts that make up the measuring
uncertainty given by Testo are listed below. When comparing the measuring
uncertainty/accuracy between manufacturers, which components are
included is to be taken into account. In many cases, not all elements that
contribute to measuring uncertainty are assessed, for example if the error
contribution of the production adjustment is shown separately or not at all.

testo 6610 - 2.3 Product description

The measuring uncertainty of the probe includes the sensor and its
electronics as well as the output of the digital measuring signal:

73

1. Linearity including scatter

2. Hysteresis

3. Reproducibility

4. Production adjustment area

5. Uncertainty of the testing

Systematic error and scattering of the
components (due to manufacturing
tolerances)

Hysteresis indicates the maximum
deviation of the readings that are
obtained when you set the same value for
the parameter, once coming from a
smaller value, once coming from a larger
value (humidity sensors actually have no
hysteresis, but rather very slow
adjustment effects that appear to be
hysteresis when considered only for a
short period.)

Repeatability (scattering of the readings
in the event of the same parameter being
entered successively)

The measuring uncertainty of the
reference instruments of the adjustment
area (including the reference instrument)
in production

Uncertainty of the procedure for
determining points 1 and 2.

74

testo 6610 - 2.3 Product description

2.3.1.3 Ordering options for testo 6610 probes
(0555 6610)

Order code Characteristic

Lxx Probe type

L 11 Probe 6611
L 12 Probe 6612
L 13 Probe 6613
L 14 Probe 6614
L 15 Probe 6615
L 17 Probe 6617
L 22 Probe 6622
L 23 Probe 6623

Mxx Protective
filter

M 01 Stainless steel sintered filter
M 02 Metal wire protection cap
M 03 Sintered Teflon filter
M 04 Open metal protection cap
M 05 ABS plastic cap (open)
M 06 Teflon filter with drip hole
M 07 Teflon filter with drip hole and condensation protector
M 08 Filter for H
Nxx Cable length
N 00 Without cable (testo 6611)
N 01 1 m cable length (testo 6613, 6614, 6615, 6617, 6623)
N 02 2 m cable length (testo 6613, 6614, 6615, 6617, 6623)
N 05 5 m cable length (testo 6613, 6614, 6615, 6617, 6623)
N 10 10 m cable length (testo 6613, 6614, 6615, 6617, 6623)
N 23 Cable length specifically for duct versions (testo 6612, 6622)
Pxx Probe length

atmospheres

2O2

testo 6610 - 2.3 Product description

Order code Characteristic

P 07 Probe length approx. 70 mm (t esto 6611)
P 12 Probe length approx. 120 mm (testo 6613)
P 20 Probe length approx. 200 mm (testo 6611, 6612, 6613,

6614, 6615, 6617, 6622, 6623)
P 30 Probe length approx. 300 mm (testo 6612, 6613)
P 50 Probe length approx. 500 mm (testo 6612, 6613, 6614,

6615, 6617, 6622, 6623)
P 80 Probe length approx. 800 mm (testo 6612, 6613)

2.3.1.4 Filters

One of the following filters or protection caps can be used for each probe
version:

Filter* Article no.** Characteristic Length A (mm)

M 01 0554 0647 Stainl ess steel sintered filter 33
M 02 0554 0757 Metal wire protection cap 40,3
M 03 0554 0759 Sintered Teflon filter 35
M 04 0554 0755 Open metal protection cap 35
M 05 0192 0265 Open ABS pl astic cap 25
M 06 0554 9913 Teflon filter with drip hole 35
M 07 0554 9913 +

0554 0166

M 08 0554 6000 Filter for H2O2 atmospheres 35

* When ordering the probe, please use this filter code, cf. Chapter 2.3.1.3 Orderin g

options for testo 6610 probes (0555 6610)

** When purchasing a replacement (filters only), please use this order number

Teflon filter with drip hole and
condensation protector

35
55

75

76

testo 6610 - 2.3 Product description

2.3.2 testo 6611 wall probe

The wireless testo 6611 probe is inserted into the testo 6681 humidity
transmitter that is mounted on the wall and ready-wired.

At a glance

1 Filter (including: humidity

and temperature sensor)
2 Probe shaft
3 Key
4 Connector

Application

• Monitoring and regulating the production and storage air quality when

manufacturing and storing hygroscopic products

• Meeting the top accuracy requirements

• Clean room applications for which a metal housing i s requi red.

E

E

L-A
A

testo 6681 transmitter

testo 6611 wall probe

L

Technical Data

Parameters

- Humidity (% °Ctd/°Ftd), etc.

- Temperature

Measuring range

- Humidity: 0 to 100 % RH

- Temperature: -20 to +70 °C/4 to

+158 °F

Material

- Probe shaft: Stainless steel

- Connector: ABS plastic

Accuracy (at 25 °C/77 °F)*

Length 200 mm
Humidity

- ± (1,0 % RH + 0.007 x reading) for

0 to 90 % RH

- ± (1,4 % RH + 0.007 x reading) for

90 to 100 % RH

- 0.02 % RH/K, dependent upon the

process temperature
(with a deviation of 25 °C/+77 °F)

- 0.02 % RH/K, dependent upon the

electronics temperature
(with a deviation of 25 °C/+77 °F)

Temperature

- ±0.15 °C (0.27 °F)

with slope PT100 1/3 class B

testo 6610 - 2.3 Product description

* Refer to the charts below for the

correlation between temperature

and accuracy.
Length 70 mm
As with length of 200 mm, but with

additional measuring error, specified
for the operating mode 2 channels at
12 mA, without display light, relay off:

Humidity: ±1.6 % RH (additional)
Temperature: ±0.6 °C / ±1.1 °F

(additional)

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

Probe dimensions

- Diameter of probe shaft: 12 mm

- E = 55 mm

- L = approx. 70 mm or 200 mm

- L – A = 35 mm or 165 mm

- A, see Table Filters,

Chapter 2.3.1.4.

77

78

testo 6610 - 2.3 Product description

Measuring accuracy of testo 6611 wall probe

Humidity error according to amount |±% RH| as a factor of process humidity

% RH

% RH

Temperature error as a factor of process temperature and temperature of
electronics

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F

testo 6610 - 2.3 Product description

2.3.3 testo 6612 duct probe

The testo 6612 probe measures the humidity and temperature in air ducts.

At a glance

1 Filter (including: humidity

and temperature sensor)
2 Probe shaft
3 Wall/duct holder

(accessories,

Order no.: 0554 6651)
4 Mounting bracket

(permanently joined to

probe shaft)
5 Probe cable
6 Key
7 Connector

79

In the event of overpressures, the probe may become a
projectile.

For assembly, see Pressure resistance on the following
page.

80

testo 6610 - 2.3 Product description

Application

• Monitoring and regulating the production and storage air quality in air

ducts when manufacturing and storing hygroscopic products

• Meeting the top accuracy requirements

• Air duct applications for which a metal housing is required.

testo 6681 transmitter testo 6612 duct probe

Technical Data

Parameters

- Humidity (% RH/°Ctd/°Ftd), etc.

- Temperature

Measuring range

- Humidity: 0 to 100 % RH

- Temperature: - 30 to +150 °C/-22

to +302 °F

Material

- Probe shaft: Stainless steel

- Line: Sheathed, FEP

- Connector: ABS plastic

Accuracy (at 25°C/77°F)*

Humidity

- ± (1,0 % RH + 0.007 x reading) for

0 to 90 % RH

- ± (1,4 % RH + 0.007 x reading) for

90 to 100 % RH

- 0.02 % RH/K, dependent upon the

process temperature
(with a deviation of 25 °C/+77 °F)

- 0.02 % RH/K, dependent upon the

electronics temperature
(with a deviation of 25 °C/+77 °F)

Temperature

- ±0.15 °C (0.27 °F)

Slope PT100 1/3 class B
* Refer to the charts below for the

correlation between temperature
and accuracy.

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

testo 6610 - 2.3 Product description

Probe dimensions

- Diameter of probe shaft: 12 mm

- L = approx. 200/300/500/800 mm

- L – A = 165/265/465/765 mm

- A, see Table Filters,

Chapter 2.3.1.4.

Cable length incl. probe shaft and
filter

- Customized for duct version

Pressure resistance

- PN 10 (probe tip)**

** If installing probe under pressure,

please use cutting ring screw
connection (order no. 0554 1795).

Measuring accuracy of testo 6612 duct probe

Humidity error according to amount |±% RH| as a factor of process
humidity

% RH

81

% RH

82

testo 6610 - 2.3 Product description

Temperature error as a factor of process temperature and temperature of
electronics

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F

testo 6610 - 2.3 Product description

2.3.4 testo 6613 cable probe

The testo 6613 probe is used when the spatial separation of the transmitter
and probe is required.

At a glance

83

1

4

5

2

1 Connector
2 Key
3 Probe cable
4 Probe shaft

3

5 Filter (including: humidity

and temperature sensor)

In the event of overpressures, the probe may become a
projectile.

For assembly, see Pressure resistance on the following
page.

Application

• Monitoring and regulating industrial humidity proce sses (apart from

high-humidity processes), e.g. food production, storing fruit

• Monitoring the production and storage air quality whe n manufacturing

and storing hygroscopic products

• Meeting the top accuracy requirements

• Clean room applications

• Applications for which a sturdy metal housing is requi red.

84

testo 6610 - 2.3 Product description

We recommend that the testo 6614 (heated) probe be used
for continuous high-humidity processes.

testo 6681 transmitter testo 6613 cable probe

Technical Data

Parameters

- Humidity (% RH/°Ctd/°Ftd), etc.

- Temperature

Measuring range

- Humidity: 0 to 100 % RH

- Temperature: - 40 to *180 °C/-40

to +356 °F

Material

- Probe shaft: Stainless steel

- Line: Sheathed, FEP

- Connector: ABS plastic

Accuracy (at 25 °C/77 °F)*

Humidity

- ± (1,0 % RH + 0.007 x reading) for

0 to 90 % RH

- ± (1,4 % RH + 0.007 x reading) for

90 to 100 % RH

- 0.02 % RH/K, dependent upon the

process temperature
(with a deviation of 25 °C/+77 °F)

L-A

A

L

- 0.02 % RH/K, dependent upon the

electronics temperature
(with a deviation of 25 °C/+77 °F)

Temperature

- ±0.15 °C (0.27 °F)

Slope PT100 1/3 class B
* Refer to the charts below for the

correlation between temperature
and accuracy.

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

Probe dimensions

- Diameter of probe shaft: 12 mm

- L = approx. 120/200/300/500/800

mm

- L – A = 85/165/265/465/765 mm

- A, see Table Filters,

Chapter 2.3.1.4.

testo 6610 - 2.3 Product description

Cable length incl. probe shaft and
filter

- 1/2/5/10 m

Pressure resistance**

- PN 10 (probe tip)

- PN 3 (if end of probe/cable is

involved in process)

** If installing probe under pressure,

please use cutting ring screw
connection (order no. 0554 1795).

Measuring accuracy of testo 6613 cable probe

Humidity error according to amount |±% RH| as a factor of process humidity

% RH

85

% RH

86

testo 6610 - 2.3 Product description

Temperature error as a factor of process temperature and temperature of
electronics

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F

% RH

testo 6610 - 2.3 Product description

testo 6614 heated cable probe
The testo 6614 heatable probe is suitable for use in high-humidity processes

in which there is the possibility of condensation for the probe.

Please also see Chapter 1.3.3.5 for the functional principle of
the testo 6614.

At a glance

87

1

2

3

6

45

1 Connector
2 Key
3 Probe cable
4 Probe shaft
5 Filter (including:

humidity and
temperature sensor)

6 Cable for temperature

probe

7

7 Temperature probe

In the event of overpressures, the probe may become a
projectile.

For assembly, see Pressure resistance on the following
page.

88

testo 6610 - 2.3 Product description

Application

• Monitoring and regulating high-humidity processes, e.g. drying

(ceramics, tobacco, wood, food) and maturing (cheese, fruit).

testo 6681 transmitter testo 6614 heated cable probe

L-A A

L

L

Assembly
distance
max. 10 cm

Technical Data

Parameters

- Humidity (% RH/°Ctd/°Ftd), etc.

- Temperature

Measuring range

- Humidity: 0 to 100 % RH

- Temperature: - 40 to +180 °C/-40

to +356 °F

Material

- Probe shaft: Stainless steel

- Line: Sheathed, FEP

- Connector: ABS plastic

Accuracy (at 25 °C/77 °F)*

Humidity

- ± (1.0 % RH + 0.007 x reading) for

0 to 100 % RH

- 0.02 % RH/K, dependent upon the

process temperature
(with a deviation of 25 °C/+77 °F)

- 0.02 % RH/K, dependent upon the

electronics temperature
(with a deviation of 25 °C/+77 °F)

Temperature probe

Temperature

- ±0.15 °C (0.27 °F)

- Slope PT100 1/3 class B

* Refer to the charts below for the

correlation between temperature
and accuracy.

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

testo 6610 - 2.3 Product description

Probe dimensions

- Diameter of probe shaft: 12 mm

- Diameter of temp. probe: 3 mm

- L = approx. 200/500 mm

- L – A = 165/465 mm

- A, see Table Filters,

Chapter 2.3.1.4.

Cable length incl. probe shaft and
filter

- 1/2/5/10 m

Pressure resistance**

- PN 10 (probe tip)

- PN 3 (if end of probe/cable is

involved in process)

** If installing probe under pressure,

please use cutting ring screw
connection (order no. 0554 1795).

Measuring accuracy of testo 6614 heated cable probe

Humidity error according to amount |±% RH| as a factor of process humidity

% RH

89

% RH

90

testo 6610 - 2.3 Product description

Temperature error as a factor of process temperature and temperature of
electronics

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F

2.3.5 testo 6615 trace humidity cable probe
(self-adjustment)

The testo 6615 probe corrects deviations in measurements by means of self­adjustment. This has a particular significance with low humidity values (in
pressure dewpoint range).

Please also see Chapter 1.3.3.6 for the functional principle of
the testo 6615.

Only use testo 6615 with sintered Teflon filter (art. no.
0554 0756) or sintered stainless steel filter (art. no.
0554 0647).

During the self-adjustment phase the signal values of the
analog outputs remain on hold, meaning they are frozen for
the duration.

At a glance

testo 6610 - 2.3 Product description

91

1

4

5

1 Connector
2 Key

2

3 Probe cable
4 Probe shaft
5 Filter (including: humidity

and temperature sensor)

3

In the event of overpressures, the probe may become a
projectile.

For assembly, see Pressure resistance on the following
page.

Application

• Monitoring and regulating trace humidity processes (compressed ai r

with adsorption or membrane driers and plastic granulate driers)

• Used when spatial separation of transmitter and probe is required.

92

testo 6610 - 2.3 Product description

testo 6681 transmitter testo 6615 trace humidity cable probe

L-A A

L

Technical Data

Parameters

- Pressure dewpoint (°Ctd/°Ftd), etc.

- Temperature

Measuring range

- Pressure dewpoint: - 60 to + 30

°Ctd/-148 to +212 °Ftd

- Temperature: - 40 to +120 °C -40

to +248 °F

(Temp. durability up to +180
°C/+356 °F)

Material

- Probe shaft: Stainless steel

- Line: Sheathed, FEP

- Connector: ABS plastic

Accuracy (at 25 °C/77 °F)*

Pressure dewpoint

- ± 1 K at 0 °Ctd/+32 °F

- ± 2 K at -40 °Ctd/-40 °F

- ± 4 K at -50 °Ctd/-58 °F

- ± 6 K at -60 °Ctd/-76 °F

Temperature

- ±0.15 °C (0.27 °F)

Slope PT100 1/3 class B

* Refer to the charts below for the

correlation between temperature
and accuracy.

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

Probe dimensions

- Diameter of probe shaft: 12 mm

- L = approx. 200/500 mm

- L – A = 165/465 mm

- A, see Table Filters,

Chapter 2.3.1.4.

Cable length incl. probe shaft and
filter

- 1/2/5/10 m

Pressure resistance

- PN 16 (probe tip)**

** If installing probe under pressure,

please use cutting ring screw
connection (order no. 0554 1795).

testo 6610 - 2.3 Product description

Measuring accuracy of testo 6615 trace humidity cable probe

Humidity error according to amount |±% RH| as a factor of process humidity

K

°Ctd

Temperature error as a factor of process temperature and temperature of
electronics

93

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F

94

testo 6610 - 2.3 Product description

testo 6617 cable probe (self-monitoring)

The testo 6617 probe is used if spatial separation of the transmitter and
probe is required, particularly for media (gases, vapours) which can
jeopardize/damage the humidity sensor (the testo 6617 has a self-monitoring
and early-warning function for such applications).

At a glance

1

2

3

4

1 Connector
2 Key
3 Probe cable
4 Probe shaft
5 Filter (including: humidity

5

and temperature sensor)

In the event of overpressures, the probe may become a
projectile.

For assembly, see Pressure resistance on the following
page.

Application

• Monitoring and regulating industrial humidity processes involving

corrosive media (apart from high-humidity processes) with the
exception of applications with HCL, HF and other acids and acidifiers
in larger concentrations (SO

• Meeting the top accuracy requirements

• Applications for which a sturdy metal housing is requi red.

, SO3, NO2)

2

testo 6610 - 2.3 Product description

This probe does NOT have a longer life with exposure to
aggressive media than the testo 6613, for example. However,
early warning of damage to the sensor is given so that
machine failures can be avoided.

2.3.5.1 Self-monitoring of cover electrode

Use in harsh ambient conditions with aggressive media in some cases incurs
the risk of damage to the sensor.

Damage to the sensor is generally reflected by incorrect readings which
occur a long time before the sensor is wrecked. If this damage to the sensor
is not spotted until too late, high costs can be incurred due to unusable
readings or machine shutdowns and waiting times until the sensor is
replaced.

1 Cover electrode
2 Bottom electrode
3 Substrate

(Ceramic substrate for
mechanical protection)

4 Connections

(protected against corrosion)

5 Dielectric layer

95

The testo 6617 has a unique self-monitoring function. This allows early
detection of damage to the sensor, e.g.:

• Mechanical damage (e.g. scratches)

• Damage from aggressive gases (e.g. acids in aerosol form)

• Welling or detachment of polymer layer due to effects of solvents.

Once the self-monitoring reaches the specific limit value, the probe warning
message "Sensor early warning" is issued.

96

testo 6610 - 2.3 Product description

testo 6681 transmitter testo 6617 cable probe (self-monitoring)

L-A A

L

Technical Data

Parameters

- Humidity (% RH/°Ctd/°Ftd)

- Temperature

Measuring range

- Humidity: 0 to 100 % RH

- Temperature: - 40 to + 180 °C/-40

to 356 °F

Material, weight

- Probe shaft: Stainless steel

- Line: Sheathed, FEP

- Connector: ABS plastic

Accuracy (at 25 °C/77 °F)*

Humidity

- ± (1,2 % RH + 0.007 x reading) for

0 to 90 % RH

- ± (1,6 % RH + 0.007 x reading) for

90 to 100 % RH

- 0.02 % RH/K, dependent upon the

process temperature
(with a deviation of 25 °C/+77 °F)

- 0.02 % RH/K, dependent upon the

electronics temperature
(with a deviation of 25 °C/+77 °F)

Temperature

- ±0.15 °C (0.27 °F)

Slope PT100 1/3 class B
* Refer to the charts below for the

correlation between temperature
and accuracy.

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

Probe dimensions

- Diameter of probe shaft: 12 mm

- L = approx. 200/500 mm

- L – A = 165/465 mm

- A, see Table Filters,

Chapter 2.3.1.4

Cable length incl. probe shaft and
filter

- 1/2/5/10 m

Pressure resistance

- PN 10 (probe tip)**

** If installing probe under pressure,

please use cutting ring screw
connection (order no. 0554 1795).

testo 6610 - 2.3 Product description

Measuring accuracy of testo 6617 cable probe (self-monitoring)

Humidity error according to amount |±% RH| as a factor of process humidity

% RH

% RH

Temperature error as a factor of process temperature and temperature of
electronics

97

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F

98

testo 6610 - 2.3 Product description

2.3.6 testo 6622 duct probe

The testo 6622 probe measures the humidity and temperature in air ducts.

At a glance

1 Filter (including: humidity

and temperature sensor)
2 Probe shaft
3 Wall/duct holder

(accessories,

Order no.: 0554 6651)
4 Mounting bracket

(permanently joined to

probe shaft)
5 Probe cable
6 Key
7 Connector

In the event of overpressures, the probe may become a
projectile.

For assembly, see Pressure resistance on the following
page.

Application

• Monitoring and regulating the production and storage air quality in air

ducts when manufacturing and storing hygroscopic products

• Meeting the top accuracy requirements

• Air duct applications for which a metal housing is required.

testo 6610 - 2.3 Product description

testo 6681 transmitter testo 6622 duct probe

Technical Data

Parameters

- Humidity (% RH/°Ctd/°Ftd), etc.

- Temperature

Measuring range

- Humidity: 0 to 100 % RH

- Temperature: - 30 to +120 °C/-22

to +302 °F

Material

- Probe shaft: Stainless steel

- Line: Sheathed, FEP

- Connector: ABS plastic

Accuracy (at 25°C/77°F)*

Humidity

- ± (1,0 % RH + 0.007 x reading) for

0 to 90 % RH

- ± (1,4 % RH + 0.007 x reading) for

90 to 100 % RH

- 0.02 % RH/K, dependent upon the

process temperature
(with a deviation of 25 °C/+77 °F)

- 0.02 % RH/K, dependent upon the

electronics temperature
(with a deviation of 25 °C/+77 °F)

Temperature

- ±0.15 °C (0.27 °F)

Slope PT100 1/3 class B
* Refer to the charts below for the

correlation between temperature
and accuracy.

Reproducibility

- Better than ±0,2 % RH

Sensor

Response time without protective
filter: t 90 max. 15 sec.

Probe dimensions

- Diameter of probe shaft: 12 mm

- L = approx. 200/500

- L – A = 165/465

- A, see Table Filters,

Chapter 2.3.1.4.

Cable length incl. probe shaft and
filter

- Customized for duct version

99

100

testo 6610 - 2.3 Product description

Pressure resistance

- PN 5 (probe tip) **

** If installing probe under pressure,

please use cutting ring screw
connection (order no. 0554 1795).

Measuring accuracy of testo 6622 duct probe

Humidity error according to amount |±% RH| as a factor of process humidity

% RH

% RH

Temperature error as a factor of process temperature and temperature of
electronics

System error 6681 + probe, electronics 25 °C/+77 °F
System error 6681 + probe, electronics -25 °C to +70 °C/-13 to +158 °F