Kobold NRF-2 User manual

NRF-2 and NRF-3
Capacitance Level & TemperatureTransducer
INSTRUCTION MANUAL
1-201326/1
measuring
•
monitoring
•
analyzing
KOBOLD Instruments, Inc.
1801 Parkway View Drive
Pittsburgh, PA 15205
Main Oce:
1.800.998.1020
1.412.788.4890
[email protected]
www.koboldusa.com
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622 Mary Street; Suite 101; Warminster, PA 18974
Phone: [phone] - Fax: [phone]
Sa[email protected] - www.cabriggs.com

2
should not be exposed to ambient temperatures below
-40°C (-40°F) or above +70°C (+160°F). Special precau-
tion 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.
METAL WALLED TANKS
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 connec-
tion fitting is non-metalic, a grounding wire must be con-
nected from the tank to the G terminal on the transmitter.
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 serviceable parts.
NON-CONDUCTIVE TANKS /SILOS
With plastic, concrete, wood, or any other non-con-
ductive walled vessels a
reference electrode must
be inserted into a tank.
Most commonly, this elec-
trode 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 electri-
cal connection must be
made between the ground
reference electrode and the
G terminal of the transmitter
(or probe housing).
When installing units with PTFE (or plastic ) coat-
ed rods or cables, be careful not to damage the
insulation. NPT threads have very sharp corners and
PTFE (or plastic) can be easily cut. In acidic and/
or conductive liquids damaged units may
malfunction and the metal rods can corrode.
DESCRIPTION
The KOBOLD series NRF-2 and NRF-3 combination
level and temperature transmitters are truly a unique
product. They are designed to measure level and
temperature of conductive and non-conductive liquids
in tanks. For level sensing, the probe measures the
change in capacitance that occurs as level changes in
the tank. For temperature sensing, the probe utilizes a
Platinum resistive element.
The level calibration is accomplished via 4 push
buttons and temperature calibration is accomplished
via two pots, located on the transmitter.
Capacitance Level Transducer
Kobold two-wire NRF level transmitters are designed
to measure either liquid or certain dry bulk media. The
RF probes operate by applying a constant voltage to a
metallic rod and monitoring the current that flows. This
current is proportional to the capacitance from the me-
tallic rod to a second electrode. Because the tank wall
is the most convenient second electrode, the sensor
monitors current to ground. The 12-30 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 chang-
es in electrical capacitance. The probe and a ground
reference electrode, usually the metal tank wall, have a
certain capacitance 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-proces-
sor 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.
INSTALLATION
UNPACKING
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 discrepancies to Kobold.
INSTALLATION LOCATION
The Kobold NRF level sensor should be located for easy
access for service, calibration and monitoring. Sensors
Fig.1
Instruction Manual
NRF-2 & NRF-3
Capacitance Level &
Temperature Transducer
Document No: Issue Date:
NRF- 10/2013
Software Rev. : Rev. Date:
11/2013
Fig. 2

WIRING Two-Power Supply Conguration
All wiring between the power supply and the transmitter should 1. Make sure the two power sources are turned off.
be done with 18 AWG to 22 AWG shielded twisted pair. The 2. Pull power supplies wires through conduit connection.
connection is made at the terminal strip within the transmitter 3. Connect the positive supply wires to the ( + ) terminal, and
enclosure. the negative supply wires to the ( - ) terminal.
Units are designed to operate on the 12 to Leave shield unattached at transmitter.
30 VDC power only. Application of 110 VAC will Connect the shield to ground at the power source.
destroy the instrument.
4. Replace the transmitter enclosure (head) cover until time to
In order to calibrate the transmitter, you must use the loop calibrate.
current meter. It should read currents in the range of 1.00 to 5. Connect positive supply wires to the positive terminal
25.00 mA, with a resolution of .01 mA. Using a meter of less of the transmitters. See Fig. 4.
resolution will somewhat reduce the calibration accuracy. 6. Connect the loop current meters in series with the negative
There are two ways to calibrate the level and temperature supply wire of level and temperature transmitters as follows:
transmitters, using 1 power supply or two power supplies. a. Negative transmitter wires to positive meter terminals.
b. Negative meter terminals to negative power source
This is highly recommended to calibrate both level and terminals.
temperature transmitters with the same method. 7. Turn ON the power supplies. The meter may read anywhere
IN ORDER TO CALIBRATE EACH TRANSMITTER, CONNECT on the scale at either end. This is normal until calibration
BOTH TRANSMITTERS TO THE POWER SUPPLY. has been completed.
NRF-2 LEVEL CALIBRATION
One-Power Supply Conguration
1. Make sure the power source is turned off.
NRF-3 LEVEL CALIBRATION
The calibration procedure for NRF-3 is the same as NRF-2, but
2. Pull power supply wires through conduit connection. in this case the temperature output may be directly connected
3. Two pairs of wires are needed. Connect the positive supply to a controller or indicator. See Fig. 5.
wires to the ( + ) terminal, and the negative supply wires to
the ( - ) terminal.
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 wires to the positive terminal of the
transmitters. See Fig. 3.
6. Connect the loop current meters in series with the negative
supply wire of level and temperature transmitters as follows:
a. Negative transmitter wires to positive meters’ terminal.
b. Negative meter terminals to negative power source
terminal.
7. Turn ON the power. The meter may read anywhere on the
scale at either end. This is normal until calibration has been
completed. Proceed to the calibration Instructions.
3
Fig. 3
Fig. 4
Fig. 5

4
TWO POINT CALIBRATION - LEVEL INCREASE Press Z UP and S UP push buttons at the same time,then
Three calibration procedures are described. Follow the one release in 1 or 2 seconds.
which fits your application. Note the following definitions used In very rare cases, a problem of calibration still may persist.
in the calibration procedures, referring to Fig 6. This is because the values of the minimum and maximum are
not properly distributed. The RESET function may have to be
performed. 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.
When you RESET the transmitter, always perform the OFFSET
after the RESET.
To avoid the possibility of a “dead zone”, L must be at least DAMPING ADJUST
two (2) inches above the end of the probe for conductive me- This feature, primarily designed for agitated tanks and factory
dia and four (4) inches above for non-conductive media. 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).
CALIBRATION PROCEDURE L-H
The ZERO, tank in L (Low) state, MUST always be calibrated
first.
Calibration procedure H-L gives the most accurate results and
is the recommended procedure in all cases. Turn the DAMP ADJ pot to max CW (neg.) direction.
1. Fill the tank to its H (100 %) level (with probe covered).
2. Depress UP or DW buttons on Z until meter reads 4.00mA.
Do not change the zero controls from now on. If changed,
the material will have to be returned to the H (100%) level.
If a 4.00mA value cannot be reached, then perform
OFFSET AND RESET functions.
3. Fill the tank to the desired H (100%) level.
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
DW buttons may be used occasionally to maintain the
loop current approximately proportional to the tank
filling or just below the 20.00 mA reading.
4. After the tank has been emptied to H (100%), depress
SPAN UP or DW buttons as required to obtain a meter
OFFSET AND RESET FUNCTIONS reading of 20.00 mA. If 20.00 mA reading has been
obtained, the calibration is complete.
OFFSET and RESET functions (or values ) are factory set. They If a 20.00mA value cannot be reached, then perform OFFSET
may have to be changed by the customer in special cases AND RESET functions and re-start the
only. Follow the procedures below. calibration.
There may seem to be a malfunction with the transmitter when
the 4-20mA power loop is activated for the first time. The mA CALIBRATION PROCEDURE L-H1
reading may be below 4mA or above 20mA and pressing the
Z and S push buttons does not change the output. The ZERO, tank in L (Low) state, MUST always be calibrated
first.
Push button may have to be depressed for up to a
minute before the value changes. Turn the DAMP ADJ pot to max CW (neg.) direction.
An OFFSET function may have to be performed. To re-OFF- 1. Fill the tank to its H (100 %) level (with probe covered).
SET the transmitter, fill the level in the tank to cover the probe.
LThe level of material which corresponds to 4.00 mA of
loop current, i.e., the 0% level
L1 a material level higher than L
H1 a material level higher than L1, but less than H
HThe level of material in the vessel which correspond
to 20.00 mA of loop current, i.e., the 100% level
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%)
H-100%
H1-Less than 100%
L1-Greater than 0%
L- 0%
Fig. 6

5
2. Depress UP or DW buttons on Z until meter reads 4.00mA. (24 - 12)
Do not change the zero controls from now on. If changed, mA = -------------- x 16 + 4 = 6.28
the material will have to be returned to the H (100%) level. (96 - 12)
The correct loop current is 6.28mA.
If a 4.00mA value cannot be reached, then perform
OFFSET AND RESET functions. 2. Depress Z-UP or Z-DW buttons on ZERO until meter
reads 8.00mA. Do not change the ZERO controls
3. Fill the tank to the highest point possible (under 100%), and from now on. If changed, the material will have to
record this level as H1. The most accurate calibration will be be returned to the L (0%) level.
obtained with the greatest separation between L and H1.
If a 6.28mA value cannot be reached, then perform OFFSET
The loop current may not rise in proportion to the lower- AND RESET functions.
ing material level in tank. Instead it may rise more rapid-
ly or more slowly than the material level. The SPAN, 3. Fill the tank to the lowest point possible (under 100%) and
S- UP or S-DW buttons may be used occasionally to record this level as H1. The most accurate calibration will be
maintain the loop current approximately proportional to obtained with the greatest separation between L and H1.
the tank emptying or just below the 20.00mA reading.
The loop current may not rise in proportion to the rising
4. To determine the loop current at L1 level use the following material level in tank. Instead it may rise more rapidly or
formula: more slowly than the material level. The SPAN, S-UP or
S-DW buttons may be used occasionally to maintain
(H1 - L) the loop current approximately proportional to the tank
mA = ------------- x 16 + 4 filling or just below the 20.00mA reading.
(H - L)
4. To determine the loop current at H1 level use the following
Example: L = 12” (30.5 cm) from the bottom of the tank formula :
H1 = 72” (183 cm) from the bottom of the tank
H = 96” (244 cm) from the bottom of the tank (H1 - L)
mA = ------------- x 16 + 4
(72-12) (H - L)
mA = -------------- x 16 + 4 = 15.43
(96 - 12) Example: L = 12” (30.5 cm) from the bottom of the tank
H1 = 72” (183 cm) from the bottom of the tank
The correct loop current is 15.43mA. H = 96” (244 cm) from the bottom of the tank
Depress SPAN S-UP or S-DW buttons as required to obtain (72-12)
a meter reading of 16.80mA. If 16.80mA reading has been mA = -------------- x 16 + 4 = 15.43
obtained, the calibration is complete. (96 - 12)
The correct loop current is 15.43mA.
If a 16.80mA value cannot be reached, then perform OFFSET
AND RESET functions and re-start the Depress SPAN S-UP or S-DW buttons as required to obtain
calibration. a meter reading of 15.43mA. If 15.43mA reading has been
obtained, the calibration is complete.
If a 15.43mA value cannot be reached, then perform OFFSET
CALIBRATION PROCEDURE L1-H1 AND RESET functions and re-start the calibration Loop.
The ZERO, tank in L (Low) state, MUST always be calibrated
first.
Turn the DAMP ADJ pot to max CW (neg.) direction.
1. Fill the tank to its L1, some point below 100% 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

6
NRF-2 TEMPERATURE TRANSDUCER 3. With the temperature standard, verify the bath temperature
and if required calculate the corresponding current output for
the transmitter.
The temperature transmitter integrated with capacitive trans- 4. Immerse the probe in the temperature bath. Make sure
mitter feature has linearized output to temperature for RTD. It the output stabilizes. With ZERO pot. adjust current output to
is factory calibrated and designed for highest performance. A 4.00mA or the corresponding current output.
linearized output for RTD’s is a unique performance feature of 5. Set the temperature bath to maximum range of the transmit-
these transmitters. ter, Ex.: 100°C = 20.00mA
6. With the temperature standard, verify the bath temperature
The output of NRF-3 is a direct connection to RTD ele- and if required calculate the corresponding current output for
ment inside the probe. Thus no calibration is required. the transmitter.
TEMPERATURE CALIBRATION 7. Immerse the probe in the temperature bath. Make sure the
output stabilizes. With the SPAN pot. adjust current output to
20.00mA or the corresponding current output.
The temperature transmitter comes factory calibrated. If you 8. Repeat steps 2 to 7 until required accuracy is reached. This
need to re-calibrate the unit, you will require the following step is necessary because of the small interaction between
equipment : Zero and Span.
• 9-36 VDC Power Supply with a milliamp indicator or Single Point Calibration ( Example : 0-100°C range )
a loop-powered calibrator.
• A temperature bath. In some cases, a single point calibration is sufficient especially
• A standard reference temperature sensor. when a process is at a fixed set point.
• Test leads 1. With a temperature standard, verify the correct process
temperature and compare it to the sensor reading.
Two Point Calibration, Min. & Max. ( Example : 0-100°C 2. If the temperature reading is below the mid-point of the
range) sensor range, use the ZERO pot. to obtain the correct
reading.
1. Connect the temperature transmitter as per the wiring dia- 3. If the temperature reading is above the mid-point of the
gram for one-power supply configuration or two-power supply sensor range, use the SPAN pot. to obtain the correct
configuration. See Fig. 3 and 4, respectively. reading.
2. Set the temperature bath to the minimum range of the trans-
mitter, Ex.: 0°C = 4.00mA
Specications
Level Specications
Accuracy : ± 1% of span
(constant liquid dielectric)
Repeatability : ± 0.1 % of span
Max. Length : 12 feet
Electrical Specications
Input Power : 12–30 VDC,
polarity protected
Output : 4–20 mA, 2-wire
Max. Loop Res.: 700 Ohm @ 24 VDC
Calibration : Via 4 push button switches
non-interactive settings
Dampening Adjust : 0 - 30 Seconds
Temperature Range
Process : –100 ...350 °F
Ambient : –58 ...140 °F
Temperature Specications
Input : Pt100, 3-wire, a = 0.00385,
DIN EN 60751
Output : 4-20 mA loop powered,
linear to temperature
Power Supply : 12-30 VDC, polarity protected
Long Term Drift : ± 0.05 % FS / year
Accuracy : 0.5 % FS
Span / Zero Adjustment :
20 turn potentiometer,
± 10 % for zero and span
Maximum Loop Resistance :
Rmax. = [ Vsupply – 9 VDC ] / 20 mA
Open Circuit Detection :
Over-scale limit ( 27.0 mA ) or
Under-scale limit ( 2.2 mA )
Temperature Range
Process : –100 ...350 °F
Ambient : –58 ...140 °F
Mechanical Specications
Enclosures : Polyamide NEMA 4,
Stainless NEMA 4X or
Aluminum NEMA 4X
Mounting Thread : 1/2”and 3/4”NPT, others
available, consult factory
Fitting Mat’l: 316 Stainless Steel
Probe Mat’l: Fully PFA clad 316
Stainless Steel
Maximum Pressure
316 SS tting : 500 PSIG @ 70°F
250 PSIG @ 300°F
100 PSIG @ 350°F
PTFE fitting : 14.7 PSIG max
• Information furnished by KOBOLD is believed to
be accurate and reliable.
However, no responsibility is assumed by KOBOLD
for its use.
• Specications subject to change without notice.