Kobold NRF User manual

aran_v02 or higher
NRF-100_KM Rev. : 1.0 16/04/2002
01/12/2002
Kobold two-wire NRF level transmitters
are designed to measure either liquid or
certain dry bulk media. The 12-36 VDC
4mA base current is the supply to the
unit. The NRF monitors level change by
converting movement of media UP or
DOWN the probe into pulse wave form
which is proportional to changes in
level. The amplifier converts this pulse
wave into 4 to 20 mA output signal. The
conversion of level movement to an
electrical signal is due to changes in
electrical capacitance. The probe and a
ground reference electrode, usually the
metal tank wall, have a certain capaci-
tance in air. As the medium displaces
the air, a change occurs because of the
difference in the dielectric constants of
the medium and air.
The NRF comes complete with the transmitter mounted in
an enclosure, fitting and probe (Fig. 1). Micro-processor
based electronics are protected and potted within a metal
housing. Calibration is made via four push buttons
(Fig. 3) as explained later. Variety of options including
Stainless or PVC housings, rigid or flexible probes (bare
or jacketed), NPT, sanitary or flange connections are
available.
Unpack the instrument carefully. Inspect all components
for damage. Report any damage to Kobold within 24
hours. Check the contents of the packing slip and report
any discrepencies to Kobold.
The Kobold NRF level sensor should be located for easy
access for service, calibration and monitoring. Sensors
should not be exposed to ambient temperatures below
-40°C (-40°F) or above +70°C (+160°F). Special precaution
should be made to prevent exposure to corrosive
atmosphere, excessive vibration, shock or physical
damage. It is preferable that the NRF is not installed in
proximity to high voltage wires or other sources of high
electrical noise.
Fig 1.
It is a common practice to use the metal tank wall as the
reference electrode. In such cases, it is required that the
probe housing makes a good electrical connection to the
tank wall. If there is any doubt about this connection due
to the use of PTFE thread tape, gaskets, paint, rust, or
any other reason, a separate grounding wire should be
installed between the probe and the tank housing. In case
the probe housing is non-metalic, or if the connection
fitting is non-metalic, a grounding wire must be connected
from the tank to the G terminal on the transmitter.
CAUTION: This unit contains CMOS electronics which
may be damaged by static electricity. Electronics may
be accessed by removing the top cover of the enclosure
(head). Do not remove the transmitter face plate (and
touch the electronics). There are no servicable parts.
With plastic, concrete, wood, or any other non-conductive
walled vessels a reference electrode must be inserted
into a tank. Most commonly, this electrode will be in the
form of a concentric, ground tube (i.e. stilling well, Fig. 2)
or a metal rod installed in parallel with the probe. In all
cases, a good electircal connection must be made
between the ground reference electrode and the G
terminal of the transmitter (or probe housing).
CAUTION: When installing units withPTFE (or plastic)
coated rods or cables, be careful not to damage the
insulation. NPT threads have very sharp corners and
conductive liquids damaged units may malfunction and
the metal rods can corrode
Fig 2.
Page 1
PTFE (or plastic) can be easily cut. In acidic and/or

aran_v02 or higher
NRF-100_KM Rev. : 1.0 16/04/2002
01/12/2002
In order to calibrate the transmitter, you must use the loop
current meter. It should read currents in the range of 1.00
to 25.00 mA, with a resolution of .01 mA. Using a meter
of less resolution will somewhat reduce the calibration
accuracy. To calibrate the instrument :
1. Remove enclosure (head) cover.
2. Connect the loop current meter as per instructions in
WIRING section(Fig. 3).
3. The loop current should now be in the range of 1.5
mA to 38 mA, which is normal at this point.
Three calibration procedures are described. Follow the
one which fits your application. Note the following defini-
tions used in the calibration procedures, referring to Fig 4.
L= the level of material which corresponds to 4.00 mA of
loop current, i.e., the 0%
L1 = a material level higher than L
H1 = a material level higher than L1, but less than H.
H= the level of material in the vessel which corres-
ponds to 20.00 mA of loop current, i.e., the 100% level.
Note: To avoid the possibility of a “dead zone”, L must be
at least two (2) inches above the end of the probe for (4)
conductive media and four inches above for non-
conductive media.
CALIBRATION L- H = when material in tank can be set
to L (0%) and H (100%).
CALIBRATION L - H1 = when material in tank can be set
to L (0%) and H1 (less than 100%).
CALIBRATION L1 - H1 = when material in tank can be
set to L1 (greater than 0%) and H1 (less than 100%).
NOTE: Calibration procedure L-H gives the most
accurate results and is the recommended procedure in
all cases.
All wiring between the power supply and the transmitter
should be done with 18 AWG to 22 AWG shielded twisted
pair. The connection is made at the terminal strip within
the transmitter enclosure.
CAUTION: Units are designed to operate on the 12 to
36 VDC power only. Application of 110 VAC will destroy
the instrument.
1. Make sure the power source is turned off.
2. Pull power supply wires through conduit connection.
3. Connect the positive supply wire to the (+) terminal,
and the negative supply to the (-) terminal.
Note: Leave shield unattached at transmitter.
Connect the shield to ground at the power source.
4. Replace the transmitter enclosure (head) cover until
time to calibrate.
5. Connect positive supply wire to the positive terminal
of the transmitter. See Fig. 3.
6. Connect the loop current meter in series with the
negative supply wire as follows:
a. Negative transmitter wire to positive meter
terminal. See Fig. 3.
b. Negative meter terminal to negative power
source termianl. See Fig.3.
7. Turn ON the power. The meter may read anywhere
on the scale at either end. This is normal until calibra
tion has been completed. Proceed to the calibration
Instructions.
Fig. 3
Page 2

aran_v02 or higher
NRF-100_KM Rev. : 1.0 16/04/2002
01/12/2002
OFFSET and RESET functions (or values ) are factory
set. They may have to be changed by the customer in
special cases only. Follow the procedures below.
There may seem to be a malfunction with the transmitter
when the 4-20mA power loop is activated for the first
time. The mA reading may be below 4mA or above
20mA and pressing the Zand Spush buttons does not
change the output.
Note : Push button may have to be depressed for up to
a minute before the value changes.
An OFFSET function may have to be performed. To
re-OFFSET the transmitter, lower the level in the tank to
below the probe. Press Z UP and S UP push buttons at
the same time,then release in 1 or 2 seconds. The trans-
mitter will now show a default value close to 4mA.
In very rare cases, a problem of calibration still may
persist. This is because the values of the minimum and
maximum are not properly distributed. The RESET
function may have to be perfomed To RESET the
transmitter, simply press Z DW and S DW push buttons
at the same time,then release the two push buttons after
1 or 2 seconds. Then re-OFFSET the transmitter as per
instructions above. The transmitter will now show a
default value close to 4mA.
Note: When you RESET the transmitter, always perform
the OFFSET after the RESET.
This feature, primarily designed for agitated tanks and
factory set at 0 sec. (max. CW, neg. direction) via a
single turn pot, sets a time delay on the output signal.
The time delay range is 0-10 sec. approx. For non-
agitated tanks a zero setting is fine. Increase the setting
for agitated tanks by turning the pot CCW. This stabilizes
the mA reading, but adds time delay. When performing
calibration, always set pot to maximum CW direction
(minimum time delay).
Turn the DAMP ADJ pot to max CW (neg.) direction.
1. Fill the tank to its L(0%) level (with probe covered).
2. Depress UP or DW buttons on Zuntil meter reads
4.00mA. Do not change the zero controls from now
on. If changed, the material will have to be returned
to the L(0%) level.
Note: If a 4.00mA value cannot be reached, then perform
OFFSET AND RESET functions
3. Fill the tank to the desired H(100%) level.
Note: The loop current may not rise in proportion to the
rising material level in tank. Instead it may ris more rapidly
or more slowly than the material level. The span, S, UP or
DW buttons may be used occasionally to maintain the loop
current approximatelly proportional to the tank filling or just
below the 20.00 mA reading.
4. After the tank has been filled to H(100%), depress
SPAN UP or DW buttons as required to obtain a meter
reading of 20.00 mA. If 20.00 mA reading has been
obtained, the calibration is complete.
Note: If a 20.00mA value cannot be reached, then
peform OFFSET AND RESET functions and re-start the
calibration
Fig. 4 Page 3

Turn the DAMP ADJ pot to max CW (neg.) direction.
1. Fill the tank to its L(0%) level (with probe
covered).
2. Depress UP or DW buttons on Zuntil meter
reads 4.00mA. Do not change the zero controls
from now on. If changed, the material will have to
be returned to the L(0%) level.
Note : If a 4.00mA value cannot be reached, then
perform OFFSET AND RESET functions
3. Fill the tank to the highest point possible (under
100%), and record this level as H1. The most
accurate calibration will be obtained with the
greatest separation between Land H1.
Note : The loop current may not rise in proportion to
therising material level in tank. Instead it may rise more
rapidly or more slowly than the material level. The SPAN,
S- UP or S-DW buttons may be used occasionally to
maintain the loop current approximatelly proportional to
the tank filling or just below the 20.00mA reading.
4. To determine the loop current at H1 level use the
following formula:
(H1- L)
mA = ------------- x 16 + 4
(H - L)
Example: L = 12” (30.5 cm) from the bottom of the tank
H1 = 72” (183 cm) from the bottom of the tank
H = 96” (244 cm) from the bottom of the tank
(72 - 12)
mA = -------------- x 16 + 4 = 15.43
(96 - 12)
The correct loop current is 15.43mA.
Depress SPAN S-UP or S-DW buttons as required to
obtain a meter reading of 15.43mA. If 15.43mA reading
has been obtained, the calibration is complete.
Note : If a 15.43mA value cannot be reached, then
perform OFFSET AND RESET functions and re-start the
calibration
aran_v02 or higher
NRF-100_KM Rev. : 1.0 16/04/2002
01/12/2002
Turn the DAMP ADJ pot to max CW (neg.) direction.
1. Fill the tank to its L1, some point above 0% level
and record this level as L1. See Fig. 4. To determine
the loop current at L1 level use the following formula:
(L1- L)
mA = ------------- x 16 + 4
(H - L)
Example: L = 12” (30.5 cm) from the bottom of the tank
L1 = 24” (61 cm) from the bottom of the tank
H = 96” (244 cm) from the bottom of the tank
(24 - 12)
mA = -------------- x 16 + 4 = 6.28
(96 - 12)
The correct loop current is 6.28mA.
2. Depress Z-UP or Z-DW buttons on ZERO until meter
reads 6.28mA. Do not change the ZERO controls
from now on. If changed, the material will have to
bereturned to the L(0%) level.
Note: If a 6.28mA value cannot be reached, then perform
OFFSET AND RESET functions
3. Fill the tank to the highest point possible (under
100%), and record this level as H1. The most
accurate calibration will be obtained with the greatest
separation between Land H1.
Note: The loop current may not rise in proportion to the
rising material level in tank. Instead it may rise more
rapidly or more slowly than the material level. The SPAN,
S-UP or S-DW buttons may be used occasionally to
maintain the loop current approximatelly proportional to
the tank filling or just below the 20.00mA reading
4. To determine the loop current at H1 level use the
following formula :
(H1- L)
mA = ------------- x 16 + 4
(H - L)
Page 4

aran_v02 or higher
NRF-100_KM Rev. : 1.0 16/04/2002
01/12/2002
Output : 4 - 20 mA , 2-wire
Maximum Loop
Resistance : 350Ωat 12VDC, 950Ωat 24VDC
Calibration : Via 4 push-button switches
Capacitance range : 10 pF to 10000 pF
Resolution : ±0.1%
Linearity Due to
Temperature : Negligible (less than 100 ppm)
Minimum Span : 10 pF
Accuracy and
Repeatability : ±1% of span or less
Output Damping : One turn pot, 0 - 10 sec. delay
Sensing System :
Operating Temperature: Electronics -40° to 70°C
Capacitance
Maximum Probe
Frequency : 1.2 Mhz
Maximum Power at : 8 mW
Hazardous Areas: Consult Factory
Power : 12 VDC - 36 VDC
Electrical Specifications :
Mechanical Specifications :
Enclosures
Standard : NEMA 4 (Polyamide)
316 SS Fitting : 500 PSI @ 70°F, 250 PSI @ 300°F
100 PSI @ 350°F
Tri-Clamp : Per tri-clamp rating
KOBOLD INSTRUMENTS, INC.
1801, Parkway View Drive, Pittsburgh, PA 15205
Telephone: [phone] • FAX : [phone]
Web site : www.koboldusa.com
Example: L = 12” (30 cm) from the bottom of the tank
H1 = 72” (183 cm) from the bottom of the tank
H = 96” (244 cm) from the bottom of the tank
(72 - 12)
mA = -------------- x 16 + 4 = 15.43
(96 - 12)
The correct loop current is is 15.43mA.
Depress SPAN S-UP or S-DW buttons as required to
obtain a meter reading of 15.43mA. If 15.43mA reading
has been obtained, the calibration is complete.
Note: If a 15.43mA value cannot be reached, then
peform OFFSET AND RESET functions and re-start the
calibration
KOBOLD INSTRUMENTS CANADA, INC.
9A de l’Aviation, Pointe-Claire, Qc H9R 4Z2
Telephone : [phone] • FAX: [phone]
Web site : www.kobold.com
Page 5
Optional: St. Steel
Aluminum w/Epoxy Paint
Process Connection : Many styles available, 3/4" NPT
standard
Maximum Pressure:
PTFE Fitting : 150 PSI @ 70°F, 0 PSI @ 300°F