Nokeval 6720 User manual

1
No 140400
Manual
Programmable
2-wire transmitter 6720
Nokeval

2
Galvanic isolated 2-wire transmitter 6720
General description:
+
-
+
-
-
DAC
4-20 mA
Sensor
Programmer
Power 10...32 V
Transmitter 6720 is exceptionally versatile and accepts
almost all common sensor inputs. You can configure it
by PC. Transmitter front has configuration connector
which connects adapter cable POL-RS-232 to serial
port of the PC. Menu based configuration program is
easy to use. By hand held programmer 6790 you can
easily control or configurate the transmitter in field
conditions. The 16 bit A/D converter enables high
accuracy. Linearity of A/D converter is 0.01 % and
conversion accuracy of output signal is 0.03 %, without
sensor linearization error. Galvanic isolation is specially
important with thermocouples but potential differencies
with other measuring circuits can be avoided also by
process input signals. Large sensor and other input
selection and versatility reduce stocking costs
significantly because the 6720 suits for most
measuring applications.
Technical specification:
Thermocouples:
Sensor Range Linearity
E -100.... 900°C < 0.2°C -50.... 900°C
J -150.... 900°C < 0.2°C -50... 900°C
K -150.... 1350°C < 0.2°C -40... 400°C (<1°C > 400 °C)
L -100.... 900°C < 0.4°C -50... 900°C
T -150... 400°C < 0.2°C -150... 400°C
N 0....1300°C < 0.2°C 0.... 1300°C
R 0....1700°C < 0.3°C 400.... 1700°C (<1°C < 300 °C)
S 0....1700°C < 0.3°C 300.... 1700°C (<1°C < 300 °C)
C (W5) 0....2200°C < 0.3°C 400.... 2200°C (<0.4°C< 400 °C)
D (W3) 0....2200°C < 0.3°C 500.... 2200°C (<1°C < 500 °C)
B 400... 1700°C < 0.3°C 400.... 1700°C
G (W) 1000.. 2200°C < 0.4°C 1000...1700°C (<3 °C >1700 °C)
Range selection freely selectable
Calibration accuracy < 0.1 % of span
Cold junction compensation< 0.05 °C /°C
Sensor wire influence < 10kΩ, negligible
RTD's Pt100: Pt100 3- or 4-wire connections,
Other RTD's Pt500, Pt1000, Ni100, Ni1000
Range -200....+700 °C (Pt100, Pt250, Pt500)
-200....+200 °C (Pt1000)
0......+175 °C (Ni100, Ni1000)
Sensor current 0,3 mA
Calibration accuracy: 0.05% of span
Linearity < 0.03 °C (-200..700°C)
Sensor error correction freely offset selection
Potentiometer input:
range 3-wire connection 50-500 Ω
2-wire connection 2-wire 0-1000 Ω
mV inputs: -100...+100 mV
Accuracy 0,02% of span
Input impedance >1 MΩ
Accuracy 0.03% of span
Linearity 0,02% of span
Process inputs: 0..20 mA, 4..20 mA, -20..+20 mA
0..5 V, 0..10 V, -10...+10V
Display scaling On whole display range
Input impedance Current: 5 Ωand voltage: 1 MΩ
Accuracy: 0.03% of span
Linearity: 0.01% of span
IR-sensors Exergen 140F-K (60°C) and 440F-K (220°C)
Range 140F-K -40..+350°C (linearized range)
Range 440F-K -30..+600°C (linearized range)
Emissivity correction selectable by PC or hand held programmer
Programming by PC or
by hand held
programmer 6790
6720
6790
Manufacturer:
Nokeval Oy,Yrittäjäkatu 12
FIN-37100 Nokia, FINLAND
Tel: [phone]
Fax: [phone]

3
60
22.5 75 10
Removable terminals < 1.5 mm²
Rail acc. to DIN 5002 (35mm)
RL=+V-10 / 0.02 (ohm)
Maximun load for output
4..20 mA
Power supply V DC
Connection and dimensions:
Output:
2-wire 4-20 mA
Straight and reversed 4-20 mA / 20-4 mA
Resolution < 0.03 % of span
Output limiter 24 mA
Sensor break monitoring 3.5 or 24 mA
Configuration:
Connection 2-pole Nokeval POL-connection
(transmitter)
Serial data RS232, 1200, 9600 bps
Serial protocol Meku 1
General:
Power supply range 10-32 VDC
Temperature effects <0.005 %/°C
Galvanic isolation 2000 VDC/ 1 min.
Measuring rate 4-5 samples/s.
AD-converter 16 bit
Output DAC 12 bit
Operating temperature 0..60 °C
Ambient storage -20....+70 °C
Humidity (non -condensing) 0..95 %RH
Maximum load See table below
Weight 80 g
Connection 1.5 mm2, AWG 16
Type 6720 - Pt100 - 0/600
Model
Sensor input
Range
Example: 6720-Pt100-0/600, sensor: Pt100,
range 0..600 °C, output 4..20 mA
Transmitter is freely programmable but if you like it
factory configured use above mentioned marking
procedure.
How to order:
Optional:
Cable for transmitter/PC POL-RS232
Configuration software MekuWin
Hand held programmer 6790
7
-
8
10
9
Thermocouple,
mV-inputs and
IR-sensors
+
-
5
7
6
-
8
10
9
mA- and Voltage
inputs
0-5/10V
0/4-20 mA
+
+
-
(Com)
Socket for
POL-RS232 cable
-
5
7
6
4
3
2
1
+
-
8
10
9
Output
4-20 mA
Pt100-sensor
3- or 4-wire*
Power supply
24 VDC
14 18 22 26 30 V
0
200
400
600
800
1000
Ohm
10
4-wire connection
(see page 7)
9
8
10
Potentiometer
3-wire connection
50-500 ohm
+
9
8
10
+
Potentiometer
2-wire connection
0-1000 ohm

4
6720
Programming by PC
RS-232
cable
Programming
Transmitter programming is simple by menu based
configuration program MekuWin by PC or by hand held
programmer 6790, connected to transmitter front plug
socket Prog. Transmitter is connected to PC serial port
with serial signal cable POL-RS232.
ByMekuWinconfigurationprogramyoucanselectsensor
type and range, input filtering and max. Change rate of
output. In addition, you can correct sensor errors by
shiftingzerolevel orbychanging input range.Programis
delivered on one diskette and it is installed by Setup
program.
MekuWin is configuration program by which you can
configure several Nokeval transmitters (Meku-protocol).
This program differs from convential programs because
it does not include setting commands, which are always
loaded from device to be configured. The big advantage
of this method is that you do not need to update the
program when you later add on new functions or new
transmitter models. The same configuration program
suits for several transmitters.
Configuration program MekuWIN
Sensor selections
Selection of outputs Quick selections:
Serial port selections
configuration windows
measurement display
contact disconnection.
Help window
assists in
selections and
tell which
settings can be
made and why.
Hardware requirement :
PC at least 486, 16Mb RAM
Operating system Windows 3.11,
Windows 95/98

5
Programming start:
Connect transmitter to PC serial port with adapter cable POL-
RS232. Do not forget to supply 24 V to the transmitter.
When you start MekuWin-program for the first time, selection
windowofcommunicationsettingsappearsautomatically.Choose
in this window COM port and communication speed (BPS).
Use automatic Baud speed selection (Auto).
Set Preamble=0, Address and Slot=0. These functions are not
used in 6720 transmitter.
Main window has green quick menu (Quick) with four buttons (if
it is not visible, choose it in pull down menu Window/Quick).
The highest button opens common computer settings window
mentioned above. Second button (Conf) makes the contact with
target device. If communication fails, check computer settings,
connection of programming cable and power supply.
Sensor selections:
When connection with transmitter exists, display shows input
settings menu. Select sensor type in Sensor. Menu texts may
change according to selected sensor type.
After selections, settings are sent to transmitter by Send+Save
button.
TyypillisetasettelutK-termoelementtille
Input signal setting:
Sensor sensor type
Bip Bipolar measurement is possible by unscaled inputs
(mV, V and mA). Measuring range covers also
negative value, f.ex. ±100mA.
4-wire 4-wire measurement is possible by inputs ohm, Pt
or Ni. You must select 4-wire measurement also
measuring card (jumper).
Lo Min. input value (process inputs). By unscaled
inputs function Lo acts as zero shift and can be
used to correct sensor error.
Hi Max. input value (process inputs). By unscaled
inputs Hi acts as input multiplier by which you can
scale input value.
Emis, Hi emission or input coefficient, 1=not in use
R0 0 °C resistance value of RTD (set Pt100=100 ohm)
Unit Celsius/Fahrenheit selection (to monitor display)
Filter digital filter, 1…0.001, 1=not in use
Slew limit limits the inputs slew rate. Defines how much the
new measurement result can differ from previous
one (measuring rate 4 times/second). This function
can be disabled by setting it on a larger value than
the measuring range or on the value 0 (default
value 0).
Pullup selection of sensor break down (ON/OFF)
Output opening of output window
Serial selection of serial signal address (not used for
6720)
Code Secret code for setting changes.Secret code
protects the transmitter against unwanted changes.
It is 6-digit numeral value. Default value is 000000
(not in use). If you happen to loose the secret code,
manufacturer will give you resetin structions for
new value.

6
Settings:
In configuration menu select input filtering and scaling
of output. Settings of input and output have
separate windows (Input, Output). In addition, serial
signal (Serial) has its own window which is needed only
when modem card is installed in transmitter (model
6725).
After sensor selection you may set various correcting
coefficients and filters.
When you install settings, notice whether your PC uses
comma or period. Erronous decimal point is not
accepted.
Thermocouple inputs TcB..TcT
Thermocouple types are marked shortly Tc + sensor,
f.ex. TcB=B-type, TcK=K-type etc.. Type K has two
ranges. Narrow range TcKn (-80…+450) has better
linearization. Broader range TcK covers whole range
(-150..+1370 C). If sensor signal is too small or too big,
the value can be corrected by Emis-value. F.ex. you
want to correct sensor value at its max. reading by +2
%. Set Emis-value 0.98. Default value is 1.
Correction of thermocouple sensor error
Thermocouples are linearized to temperature.
Sometimes you need to correct sensor signal. By IR-
thermopile sensor this need depends on the emissivity
of target device.
Emis-coefficient has following effect:
Difference between measured temperature value and
cold junction temperature is divided by Emis-value and
the result is added to coldjunction temperature. Finally
Lo-value is added. Emis is reverse value of slope and
its corner point is cold junction temperature or
environment temperature of transmitter.
Tcj = transmitter environment temperature (abt.)
Ts = Uncorrected sensor temperature measured by
transmitter
Tn = corrected temperature to display; true
temperature
6720 calculates Tn = (Ts-Tcj) / (Emis + Tcj + Lo).
The use of slope to correct sensor error (one point
correction): Set Emis = 1, Lo = 0.
Heat sensor to calibration temperature. Measure true
sensor temperature Tn and temperature Ts measured
by 6720. Calculate: Emis = (Ts-Tcj) / (Tn-Tcj)
F.ex. true sensor temperature Tn = 27 °C. Temperature
measured by transmitter Ts = 895 °C. Set Correction
coefficient Emis = (895-27 °C) / (900-27) = 0.9942. At
high temperatures cold junction temperature effect is
very small in Emis calculation. You may measure cold
junction temperature Tcj easily by connecting jumper to
sensor input. 6720 shows its cold junction temperature
at terminal block.
Temperature measurement with RTD´s
Temperature sensors Pt100, Pt250, Pt1000 and Ni100
are available. Sensor connection 3- or 4-wire.
4-wiring requires jumper setting on circuit board, see
picture on page 7.
You can change sensor type by R0-value to
Pt100…Pt1000 sensor only by giving resistance value
in 0 °C, f.ex. for Pt100 sensor R0 = 100.0 ohm or for
pt250 sensor R0 = 250.0 ohm etc..
Calibration and error correction of RTD's
6720 assumes that sensor resistance in 0 °C is exactly
R0-setting. This means that 6720 compares sensor
resistance always with R0-setting. If 6720 shows too
high temperature measured by the individual sensor,
the sensor resistance is higher than nominal and you
must increase R0-value.
Advantage of this method is that also sensors can be
calibrated by giving the real measured resistance in 0
°C. F.ex. if sensor resistance in 0 °C is 100.1 ohm, R0-
value will be 100.1 ohm.
Eliminating sensor tolerance may be done, if necessary,
also in other than 0 °C temperature. Because Platin
resistance sensors are not fully linear, you have to
calculate R0-value according to equation below (other
than 0 °C temperature corrections) when high accuracy
is requested.
Selection of output signal range.
Open output window by Out-button
Lo scaled input value corresponding output 4.00 mA
Hi scaled input value corresponding output 20.00 mA
Mode limits output to 4.00/20.00 mA or to 3.5/24.0 mA
when input exceeds or remains below measuring range
Break output up or down after sensor break
Send send settings to transmitter

7
R0 = valid R0-setting (f.ex. Pt100=100)
Ron = corrected R0-setting (equation below)
Ts = Uncorrected sensor temperature measured by
transmitter
Tn = corrected temperature to display; true
temperature
Kpt = Temp. coefficient of platin in RTD-table
corresponding temp. in question (abt. 0.385
ohm/°C)
Calculate new R0:
Ron = R0 * ( Ts * Kpt + 1 ) / (Tn * Kpt + 1)
F.ex. Sensor true temp. Tn = 100 °C and 6720 shows
Ts = 99.7 °C, R0 = 100 (basic value).
Calculate correction Ron = 100 * ( 99.7 * 0.385 + 1 /
(100 * 0.385 + 1) = 99.71
Potentiometers
Potentiometer resistance value is 50…500 ohm by 3-
wire connection and 0…1000 ohm by 2-wire
connection. When potentiometer glide moves from one
end to the other of the potentiometer range , display
value turns into Lo…Hi.
As you do not always use the whole potentiometer
range, this must be noticed in scaling. The easiest way
is to exploit output scaling as follows: set in input
window f.ex. Lo=0 and Hi=100. Drive potentiometer
from beginning to end and notice display values of 6720
(monitor). Set these values in output window as Lo- and
Hi-values of mA-output.
When performing variable resistance measurement
(0…1000 ohm), the scaling is done like in point Abs.
sensor inputs.The sensor selection in menu = ohm.
0/4..20 mA and 0..5/10V process inputs
Input ranges: 0-5V, 0-10V, 0-20mA, 4-20mA. When
process signal is selected, scale the input first directly
as engineering units on monitor display. Set min. (Lo)
and max. (Hi) corresponding value, f.ex. input 0-10V
corresponds in display range 200-500. Set Lo=200 and
Hi=500 (output range is set in its own window). In case
of V-input, the jumper of the measuring card must be in
position 1-2 (mV-inputs do not need jumper setting).
Abs. inputs V, ±10 V, 20 mA and ohm
The abs. inputs as not scale in the same way as
process inputs simply by giving wanted display values to
monitor-display. In abs. inputs Hi-setting acts as
coefficient to which Lo-value is added. If input starts
from zero set Lo = 0 V (Ma, ohm), input is multiplied in
this case only by Hi-value.
You may select bipolar input by making cross to square
(Bip) in menu. If you do not need bipolar input, select
always unipolar input because then max. resolution of
A/D-conversion (1/64000) is available.
mV-inputs
mV inputs may be uni- or bipolar on range +-100 mV
(Bip). Unipolar range is more accurate because max.
resolution of A/D-conversion (1/64000) is available.
SelectionBip=Bipolar.
Infrared-sensors
Non contacting IR-sensor ranges are linearized on
whole measuring range for sensor types Exergen
140F-K (-40..+350°C) and 440F-K (-30..+600°C).
Emission coefficient corrects measured value to show
true temperature according to emissivity of target
object. Exergen sensors are calibrated for emission
coefficient 0.9 (grey body). If object emision coefficient
is 0.7 set Emis-value 0.7/0.9 = 0.77.
More details in point Thermocouple and IR-sensor
correcting coefficients (experimental Emis-control).
Other settings
Bip: Bipolarmeasurementis possible byunscaledinputs
(mV, V and mA). Measuring range covers also negative
value, f.ex. ±100mA.
4-wire: 4-wire measurement is possible by inputs ohm,
Pt or Ni. You must select 4-wire measurement also
measuring card (jumper).
Lo: Min. input value (process inputs, f.ex. 4 mA). By
unscaled inputs function Lo acts as zero shift and can
be used to correct sensor error. Value is given in
engineering unit f.ex. -5 °C. Zero shift is added first
eventually set Hi-coefficient.
Hi: Max. input value (process inputs, f.ex. 20 mA). By
unscaled inputs Hi acts as input multiplier by which you
can scale input value.Lo: You may correct sensor error
by zero shift.Value is given in sensor units, f,ex. -5 °C.
Zero shift is added first after eventually set Hi-value.
Emis: Emission or input multiplier, 1 = multiplier 1.
R0: RTD's 0 °C resistance value (f.ex. set Pt100 = 100
ohm)
Unit: C/F selection only with temperature sensors (Tc/
Pt/Ni).
Filt: filter
Notinuse=1.000.Normalfiltering0.200means(1/0.2=5)
thatthelatestmeasurementincludesonenewandfourold
measurements. Diminishing the filter value increases the
damping effect. Filtering behaves like RC-circuit.
Slew: slew rate
One measurement can not change measuring result
more than slew-value allows.
It can be used to eliminate interference peaks. One
measurement lasts abt.0.25 second so if slew value is
1, the measuring result can raise 4 units in one second
(f.ex. 4C/s). If you prefer not to to use this limiter, set
value larger than measuring range or value 0.

8
Pullup: sensor break pullup
If pullup is set on, a weak current is fed from time to
time to sensor line in order to find out eventual sensor
breaks. Function does not work with process signals (V,
mA). In these signals internal pulldown leads input to 0
V or to 0 mA.
Pullup is not recommended with high impedance
sensors (f.ex. Exergen) because the feeding of
intermittent current to sensor line disturbs measuring
(capacitive charge). By RTD´s pullup is useful for wire
breaks; sensor break is always detected.
Serial: You can set transmitter address when optional
card for digital communication is installed.
Optional card changes transmitter to model 6725.
Default value 0.
Code: secret code for setting changes
Secret code protects the transmitter against unwanted
changes. It is 6-digit numeral value. Default value is
000000 (not in use). If you happen to loose the secret
code, the manufacturer will give you reset instructions
for new setting.
Output settings:
Lo: Scaled input or sensor value corresponding to
output 4.00 mA
Hi: scaled input or sensor value corresponding 20.00
mA. Value can be anything inside selected sensor
measuring range.If input is scaled process signal output
Lo and Hi value are set in engineering units f.ex. input
0-10V=0-1000, output wanted 0-900=4-20mA, set Lo=0
and Hi=900.
Mode: selection of output function range
Limit: output limited to 4..20 mA, also after
sensor break
Full: functions abt. 3.5..24 mA and indicates
therefore range exceeding and
sensor break
Off: gives always firm value 4.00 mA. It is used
only for test purposes
Break: direction of output after sensor break
DScale: in fault situation leads output to value
<4mA
UScale: in fault situation leads output to value >20
mA (or 20.00 mA if Mode=Limit)
3 2 1
Jumper selections of input card Voltage input 0-10V:
Jumper selection 1-2
(Factory setting)
4-wire RTD-sensors:
Jumper selection 2-3
4-wire connection of voltage input (10V)
and of resistance measurement on
measuring card
Unusual sensor inputs require jumper selection on
measuring card. Open the right hand cover of the
transmitter. You can easily remove measuring card from
basic board. Select jumper position according to picture
below.

9
Hand held programmer 6790
You can easily program transmitters with hand held
programmer which is particularly useful in field
conditions. Menu structure is similar to PC-program.
Programmer is simply connected to transmitters plug
socket Prog with cable. Programmer is universal and
does not include configuration program which is loaded
from transmitter to be configured.
The use of programmer
When you have swicthed on 6790, display shows text
Conn. Set first serial communication baud rate 9600
(Baud) and then Slot setting value 0 (default value).
Address is not needed.
Switch on power supply 24 V and connect cable to
transmitter plug socket Prog. Now you can start loading
of configuration program from transmitter by pushing ➤
button. Loading takes a few seconds. If sensor is
connected to transmitter, display shows sensor
measuring value. An open input may show random
values.
Start programming by pushing Conf-button until the
menu shows text Sensor. If you like to change sensor
push ➤button and make changes by ▲ ▼ buttons.
After selection come back to main level by
❉-button.
Settings are sent or canceled in Save or Undo stage by
➤ button.
Input settings:
Sensor Selection of sensor type.
Bip Bipolar measurement is possible by unscaled inputs
Measuring range covers also negative value.
4-wire ohm-, Pt ja Ni-sensor 4-wire connection
Lo Zero shift (sensor calibration if necessary).
Hi Scaling of input (only mA- and V-inputs).
Emis Emission or input coefficient, 1 = not in use.
R0 RTD's 0 °C resistance value (set Pt100=100 ohm).
Unit Selection of Celsius/Fahrenheit (monitor näytölle).
Filter Digital filter, 1...0.001, 1 = not in use.
Slew limit Limiter of slew rate. One measurement can not change
measuringresultmorethanslew-valueallows(measuringrate
is 4 times/second). If you do not want to use it, set value 0 or
larger than measuring range.
Pullup Selection of sensor break sensing (ON/OFF).
Code Setting of secret code. You can not change settings without
secret code if it is set to other than default value 000000.
Selection of output range:
Select wanted part of input sensor range or of scaled mA-
or V-input (on display) F.ex. input 0..10V = display 0..2000,
output range 0..1500 = 4..20 mA.
Out Output setting menu.
Lo Input value (on display) corresponding output 4.00mA
Hi Input value (on display) corresponding output 20.00 mA
Mode Limits output to value 4.00/20.00 mA, or to 3.5/24.0 mA
when input goes over or below measuring range.
Break State of output after sensor break (➤➤
➤➤
➤), up or down.
Serial Do not change address, default value 0 (used for optional
card only).
Save Exit programming stage by ❉ button and save
settings to transmitter by ➤➤
➤➤
➤button.
Undo Cancel settings and exit without saving by ➤➤
➤➤
➤button.
Settings are described in more details on pages 6 and 8.
Lo
Hi
Ro
Emis
Unit
*
Filter
Slew
Pullup
Out
Sensor
Serial
Code
Lo
Hi
Adress
Mode
Break
Save
Undo
*
*
Slot
Conn
➤
Baud
Address
Conf
▼▲
▼▲
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
You can
move on or
change
numbers and
values in
programming
menu
Pt100
Load configuration program
from transmitter
*
Select sensors
Start programming by pushing
Conf -button
On
Start
Set programmer
baud rate
Set value 0
No in use

10
Notes: