TESTO 6681 Profibus User manual

testo 6681 · Humidity transmitters
testo 6610 · Probes
P2A software · Parameterizing, adjusting and analyzing
software
Instruction manual Volume 1 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 purposes.
►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
3
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!:
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®7, 8 and 10.

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.:
1Loosen and remove housing screws.
2Remove the upper part of housing.
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.
" to "
Example entries are in inverted commas, e.g.:
The value "0" results in ....
Bold type 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].
CAPITAL
LETTERS Keys on the instrument or keypad, e.g.:
Press ESC.

Contents
5
Contents
1TRANSMITTER............................................................................................6
1.1 Specifications...........................................................................................6
1.1.1 Functions and use.......................................................................6
1.1.2 Scope of delivery ........................................................................6
1.1.3 Accessories.................................................................................7
1.1.4 Technical Data............................................................................7
1.1.5 Dimensions .................................................................................8
1.2 Product description..................................................................................9
1.2.1 At a glance ..................................................................................9
1.2.2 Usable probes...........................................................................10
1.2.3 Display and keypad...................................................................10
1.2.4 Service interface .......................................................................10
1.2.5 Relay board (option) .................................................................10
1.2.6 Analog outputs ..........................................................................11
1.2.7 Parameters ...............................................................................12
1.2.8 Scaling ......................................................................................12
1.2.9 Alarm handling ..........................................................................15
1.3 Commissioning ......................................................................................16
1.3.1 Assembling the instrument .......................................................16
1.3.2 Connecting the instrument........................................................19
1.3.3 Adjusting the instrument ...........................................................31
1.4 Operation ...............................................................................................41
1.4.1 Relationship between user menu and mini-DIN socket is active
..................................................................................................41
1.4.2 Key cover ..................................................................................42
1.4.3 Password protection .................................................................43
1.4.4 Structure of user menu .............................................................43
1.4.5 Overview of the testo 6681 user menu ...........................................45
1.4.6 The individual main menus .......................................................47
1.5 Status, warning and error messages.....................................................59
1.5.1 Status messages ......................................................................59
1.5.2 Warning messages ...................................................................60
1.5.3 Error messages.........................................................................62
1.5.4 Handling alarm messages ........................................................63
1.5.5 Namur fault conditions ..............................................................65
1.6 Maintenance and cleaning.....................................................................66
1.6.1 Maintaining the instrument........................................................66
1.6.2 Cleaning the instrument............................................................66

6
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 volume 2, chapter 2for information about
commissioning, operating and maintaining the testo 6610
probe.
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.
1.1.2 Scope of delivery
The scope of delivery of the testo 6681 humidity transmitter includes the
following:
•Key cover
•Rear panel bracket

testo 6681 - 1.1 Specifications
7
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 volume 2, chapter 4.2 or on the website at
www.testo.com.
1.1.4 Technical Data
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)
Voltage supply
-2-wire: 18 to 24 V DC ± 10%
-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)

8
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
--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: 2014/130/EC
1.1.5 Dimensions
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
9
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
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

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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;
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 -70 bis +180 °C/-94...+356 °F
testo 6614 0555 6610-L14 Heated cable probe version; accuracy to
± 1.0 % RH; temperature range -40 °C to +180 °C/
-40 to +356 °F
testo 6615 0555 6610-L15 Trace humidity cable probe version;
dew point to -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; temperature range -40 °C to +180 °C/-40
to +356 °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.
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

testo 6681 - 1.2 Product description
11
•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
•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 option or with the background
lighting of the optional display are only possible in 4-wire
operation.

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testo 6681 - 1.2 Product description
1.2.7 Parameters
The following parameters are displayed:
•Relative humidity in %RH (technical)
•Relative humidity in % WMO* (calculation according to the WMO
standard)
•Temperature °C and °F
•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 "H2O (inch H2O)
•Water content in ppmvol and % vol
•Dewpoint of H2O2mixture in °Ctm and °Ftm
•Mixture humidity H2O2in %RHm
* It is possible that condensation appears as of a displayed humidity
starting from 70 % and is shown on the display. This unit is used in
meteorology, for example. According to the WMO, the Magnus
coefficient is used for sub-cooled water in the calculation of relative
humidity.
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:
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

testo 6681 - 1.2 Product description
13
- 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:
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.
However, the physical measurement range limits are the deciding
factor when defining alarms.
Parameter
Unit
probe
Measuring
range
Physical
at 1013 hPa
Standard
scaling
MUF
measuring
range
MIN
MAX
MIN
MAX
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
-70
+180
-40
+180
°F
6613
-94
+356
-40
+356
°C
6614, 6617
-40
+180
-40
+180
°F
6614, 6617
-40
+356
-40
+356
°C
6615
-40
+120
-40
+120
°F
6615
-40
+248
-40
+248
relative humidity
% RH
0
+100
0
+100
WMO relative humidity
% RH,
0
+100
0
+100

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testo 6681 - 1.2 Product description
Parameter
Unit
probe
Measuring
range
Physical
at 1013 hPa
Standard
scaling
MUF
measuring
range
MIN
MAX
MIN
MAX
Dewpoint
°Ctd
6611
-20
+70
-80
+100
°Ftd
6611
-4
+158
-112
+212
°Ctd
6612, 6613, 6614,
6617
-
20
+100 -80 +100
°Ftd
6612, 6613, 6614,
6617
-
112
+212 -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
9500
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

testo 6681 - 1.2 Product description
15
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:
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".

16
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 probes)
Attaching rear panel bracket
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.
1

testo 6681 - 1.3 Commissioning
17
Fastening instrument to rear panel bracket
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.
5

18
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.

testo 6681 - 1.3 Commissioning
19
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.
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
1 Loosen screw connection (1) of service flap and open the flap.

20
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.