Pfeiffer Vacuum PKR 261 User manual

BG 5157 BEN / C
(
2017-07
)
OPERATING INSTRUCTIONS
Translation of the original instructions
PKR 261
Compact FullRange® Gauge, All-metal

2BG 5157 BEN / C (2017-07) PKR261.oi
In all communications with Pfeiffer Vacuum, please specify the information given
on the product nameplate.
This manual applies to products with the following part numbers
PT R26 250 (DN 25 ISO-KF)
PT R26 251 (DN 40 ISO-KF)
PT R26 252 (DN 40 CF-F)
The part number can be taken from the nameplate.
We reserve the right to make engineering changes without notice.
The Compact FullRange®Gauge PKR 261 has been designed for vacuum meas-
urement in a pressure range of 5×10-9 ... 1000 hPa.
It must not be used for measuring flammable or combustible gases in mixtures
containing oxidants (e.g. atmospheric oxygen) within the explosion range.
The gauge can be used with a Pfeiffer Vacuum measurement unit for Compact
Gauges or with another evaluation unit.
Over the whole measurement range, the measuring signal is output as logarithm of
the pressure.
The PKR 261 gauge consists of two separate measurement systems (Pirani sys-
tem and cold cathode system according to the inverted magnetron principle). They
are combined in such a way that for the user, they normally behave as one uniform
measurement system.
FullRange®Pfeiffer Vacuum GmbH
Product identification
Validity
Intended use
Functional principle
Trademark

BG 5157 BEN / C (2017-07) PKR 261 3
Contents
Product identification 2
Validity 2
Intended use 2
Functional principle 2
Trademark 2
1Safety 4
1.1 Symbols used 4
1.2 Personnel qualifications 4
1.3 Safety information 4
1.4 Liability and warranty 5
2Technical Data 6
3Installation 9
3.1 Vacuum Connection 9
3.1.1 Removing the Magnet Unit (Only for Gauges With CF Flanges) 10
3.2 Electrical Connection 11
3.2.1 Use With a Pfeiffer Vacuum-Measurement Unit 11
3.2.2 Use With Another Evaluation Unit 11
4Operation 13
4.1 Measurement Principle, Measurement Behavior 13
5Maintenance 15
5.1 Adjusting the Gauge 15
5.2 Cleaning the Gauge / Replacing Parts 16
5.2.1 Disassembling the Gauge 17
5.2.2 Cleaning the Gauge 18
5.2.3 Reassembling the Gauge 19
5.3 What to do in Case of Problems 20
6Removing the Gauge From the Vacuum System 21
7Returning the Product 22
8Accessories 22
9Spare Parts 23
10 Disposal 23
Appendix 24
A: Conversion Table for Pressure Units 24
B: Relationship Between Measuring Signal and Pressure 24
C: Gas Type Dependence 25
ETL Certification 27
For cross references to pages within this manual, the symbol (→XY) is used, for
references to other documents, the symbol (→[Z]).

4BG 5157 BEN / C (2017-07) PKR261.oi
1 Safety
DANGER
Information on preventing any kind of physical injury.
WARNING
Information on preventing extensive equipment and environmental damage.
Caution
Information on correct handling or use. Disregard can lead to malfunctions or
minor equipment damage.
Skilled personnel
All work described in this document may only be carried out by persons who
have suitable technical training and the necessary experience or who have been
instructed by the end-user of the product.
•Adhere to the applicable regulations and take the necessary precautions for the
process media used.
Consider possible reactions between the materials (→6) and the process
media.
Consider possible reactions of the process media due to the heat generated by
the product.
•Adhere to the applicable regulations and take the necessary precautions for all
work you are going to do and consider the safety information in this document.
•Before you begin to work, find out whether any vacuum components are con-
taminated. Adhere to the relevant regulations and take the necessary precau-
tions when handling contaminated parts.
DANGER
DANGER: magnetic fields
Strong magnetic fields can disturb electronic devices like heart
pacemakers or impair their function.
Maintain a safety distance of ≥10 cm between the magnet and the
heart pacemaker or prevent the influence of strong magnetic fields by
antimagnetic shielding.
Pass on the safety information to other users.
1.1 Symbols used
1.2 Personnel qualifications
1.3 Safety information

BG 5157 BEN / C (2017-07) PKR 261 5
Pfeiffer Vacuum assumes no liability and the warranty becomes null and void if the
custodian or third parties
•disregard the information in this document
•use the product in a non-conforming manner
•make any kind of changes (modifications, alterations etc.) to the product
•use the product with accessories not listed in the corresponding product
documentation.
The custodian assumes the responsibility in conjunction with the process media
used.
Gauge failures due to contamination or wear and tear, as well as expendable parts
(e.g. filament), are not covered by the warranty.
1.4 Liability and warranty

6BG 5157 BEN / C (2017-07) PKR261.oi
2 Technical Data
Admissible temperature
Storage
Operation
Bakeout
-40 °C ... +65 °C
+ 5 °C ... +55 °C (up to 150 °C at the
flange if mounted horizontally; without
magnetic shielding)
+150 °C (without electronics and
magnetic shielding)
Relative humidity max. 80% up to +31 °C
decreasing to 50% at +40 °C
Use indoors only
altitude up to 2000 m (6600 ft.)
Measuring range (air, N2) 5×10-9 ... 1000 hPa
Accuracy ≈± 30%
in the range 1×10-8 ... 100 hPa
Reproducibility ≈± 5%
in the range 1×10-8 ... 100 hPa
Gas type dependence →Appendix C
Adjustment (→15)
Pirani measurement circuit
Trimmer potentiometer <HV> at < 1×10-4 hPa
(while depressing the tactile switch)
Trimmer potentiometer <ATM> at atmospheric pressure
Cold cathode measurement circuit no adjustment (the gauge is factory
calibrated and requires no mainte-
nance)
Degree of protection IP 40
Maximum pressure (absolute) 1000 kPa
only for inert gases < 55 °C
Supply
DANGER
The gauge may only be connected to supply or measurement units
that conform to the requirements of a grounded protective extra-low
voltage (PELV). The connection to the gauge has to be fused. 1)
Voltage at the gauge 15.0 ... 30.0 V= (ripple max. 1 V
pp
)
Power consumption ≤2 W
Fuse1) ≤1 AT
The minimum voltage of the power supply must be increased proportionally to the
length of the measuring cable.
Voltage of the supply unit at
maximum cable length 16.0 ... 30.0 V= (ripple max. 1 V
pp
)
Electrical connection Hirschmann compact connector
type GO 6, 6 poles, male
Tightening torque ≤0.2 Nm
Cable 5 poles plus screening
maximum cable length 75 m (0.25 mm² conductor)
100 m (0.34 mm² conductor)
300 m (1.0 mm² conductor)
1) Pfeiffer Vacuum measurement and control units for Compact Gauges fulfill these requirements.

BG 5157 BEN / C (2017-07) PKR 261 7
Operating voltage
(in the measuring chamber) ≤3.3 kV
Operating current
(in the measuring chamber) ≤500 µA
Output signal (measuring signal)
Voltage range ≈0 V ... ≈+10.5 V
Voltage/pressure relationship logarithmic, increase 0.6 V / decade
(→Appendix B)
Error signal <0.5 V (no supply)
>9.5 V (Pirani measurement element
defective, filament break)
Output impedance 2×10 Ω
Minimum load 10 kΩ, short-circuit proof
Response time pressure dependent
p > 10-6 hPa
p = 10-8 hPa
≈10 ms
≈1 s
Gauge identification →Figure 1
Pirani-only mode 11.1 kΩresistor referenced to supply
common
Combined Pirani/cold cathode mode 9.1 kΩresistor referenced to supply
common
The following conditions must be
fulfilled:
Polarity The polarity of pin 1 referenced to
supply common is always positive.
Measurement
with constant current
with constant voltage
measurement current within range
0.2 ... 0.3 mA
measurement voltage within range
2 ... 3 V
Grounding concept →Figure 1
Vacuum flange–measuring common connected via 10 kΩ
(max. voltage differential
with respect to safety ±50 V
with respect to accuracy ±10 V)
Supply common–signal common conducted separately; differential
measurement recommended for cable
lengths (≥6 m)

8BG 5157 BEN / C (2017-07) PKR261.oi
Materials exposed to the vacuum
Flange
Measuring chamber
Feedthrough isolation
Internal seals
Anode
Ignition aid
Pirani measuring tube
Pirani filament
stainless steel (1.4104)
stainless steel (1.4104)
ceramic (Al2O3), glass
Ag, Cu, soft solder (Sn, Ag)
Mo
stainless steel (1.4310 / AISI 301)
Ni, Au
W
Internal volume ≈20 cm³
Dimensions [mm]
DN 25 ISO-KF
Compact
Full RangeTM
Gauge
VACUUM
VACUUM
122.5
18
ø 63.5
32 5715.5 20
Weight 700 g
Materials exposed to the vacuum
Flange
Measuring chamber
Feedthrough isolation
Internal seals
Anode
Ignition aid
Pirani measuring tube
Pirani filament
stainless steel (1.4306/AISI 304L)
stainless steel (1.4104)
ceramic (Al2O3), glass
Ag, Cu, soft solder (Sn, Ag)
Mo
stainless steel (1.4310 / AISI 301)
Ni, Au
W
Internal volume ≈20 cm³
Dimensions [mm]
DN 40 CF-F DN 40 ISO-KF
Compact
Full RangeTM
Gauge
VACUUM
VACUUM
128.5
123
18.5
24
ø 63.5
2032 5715.5
Weight 750 g (DN 40 ISO-KF flange)
995 g (DN 40 CF-F flange)
PT R26 250 (DN 25 ISO-KF)
PT R26 251 (DN 40 ISO-KF)
PT R26 252 (DN 40 CF-F)

BG 5157 BEN / C (2017-07) PKR 261 9
3 Installation
Caution
Caution: vacuum component
Dirt and damages impair the function of the vacuum component.
When handling vacuum components, take appropriate measures to
ensure cleanliness and prevent damages.
The gauge can be mounted in any orientation. However, it should be mounted so
that any particles present cannot enter the measuring chamber (→14). If it
should be possible to operate the gauge with a maximum temperature of 150 °C at
the flange, mount the gauge horizontally.
See the dimensional drawings for space requirements (→8).
Remove the protective cap.
The protective cap will be
needed for maintenance.
Make the flange connection.
When making CF flange
connections, it can be
advantageous to temporarily
remove the magnet
(→section 3.1.1).
If it should be possible to adjust the gauge while it is connected to the
vacuum system, make sure the two <HV> and <ATM> trimmer potentio-
meters are accessible for a screw driver.
DANGER
DANGER: overpressure in the vacuum system >250 kPa
KF flange connections with elastomer sealing rings (e.g.
O-rings) cannot withstand such pressures. Process media can
thus leak and possibly damage your health.
Use sealing rings provided with an outer centering ring.
DANGER
DANGER: overpressure in the vacuum system >100 kPa
If clamps are opened unintentionally injury can be caused by
catapulted parts.
Use the type of clamps which can only be opened and closed
by means of a tool (e.g. hose clip clamping ring).
3.1 Vacuum Connection
Procedure

10 BG 5157 BEN / C (2017-07) PKR261.oi
DANGER
The gauge must be electrically connected to the grounded
vacuum chamber. The connection must conform to the re-
quirements of a protective connection according to EN 61010:
•CF flanges fulfill this requirement
•For gauges with KF flanges, use a conductive metallic
clamping ring.
WARNING
WARNING: electric arcing
Helium may cause electric arcing with detrimental effects on the
electronics of the product.
Before performing any tightness tests put the product out of
operation and remove the electronics unit.
•Allen wrench AF 1.5
•Open-end wrench AF 7
2
1
3
4
7
Unfasten the hexagon socket set screw (1) on the side of the electronics
unit (2).
Remove the electronics unit without twisting it.
Unfasten the hexagon head screw (3) on the magnet unit (4) and remove
the magnet unit.
Caution
The magnetic force and the tendency to tilt make it more
difficult to separate the magnet unit and the measuring chamber
(7).
Make the flange connection between the gauge and the vacuum system.
Remount the magnet unit and lock it with the hexagon head screw (3).
3.1.1 Removing the Magnet
Unit (Only for Gauges
With CF Flanges)
Tools required
Procedure

BG 5157 BEN / C (2017-07) PKR 261 11
Carefully mount the electronics unit (2). (Make sure the pin of the Pirani ele-
ment is properly plugged into the corresponding hole of the electronics unit.)
Push the electronics unit up to the mechanical stop and lock it with the
hexagon socket set screw (1).
If the gauge is used with a
Pfeiffer Vacuum measurement
unit for Compact Gauges, a
corresponding connection cable
is required (→22).
•Secure the connection
socket on the gauge with the
screw (tightening torque
≤0.2 Nm).
Compact FullRangeTM Gauge
VACUUM
The gauge can also be operated with other evaluation units. In this case, an
individual connection cable must be made.
For cable lengths up to 10 m (0.34 mm² conductor cross-section), the measuring
signal can be read directly between the positive signal output (pin 2) and the
supply common (pin 5) without the degree of accuracy being reduced. For longer
measuring cable lengths, we recommend a differential measurement between the
signal output and signal common (pin 3) (as a result of the voltage drop along the
supply cable ground lead, the common mode signal is approx. 1.0 V at the max.
permissible cable length).
Prepare the connection
socket (ordering number
→22).
3.2 Electrical Connection
3.2.1 Use With a
Pfeiffer Vacuum-
Measurement Unit
3.2.2 Use With Another
Evaluation Unit
Procedure

12 BG 5157 BEN / C (2017-07) PKR261.oi
Solder the connection cable according to the diagram.
10
10
Ident
2
3
1
4
5
6
V–
+
–
+
10k
Figure 1: Electrical connection
Pin 1 identification
Pin 2 signal output
(measuring signal)
Pin 3 signal common
Pin 4 supply
Pin 5 supply common
Pin 6 screen
2
5
31
6
4
Connection socket
soldering side
WARNING
The supply common (pin 5) and the screen (pin 6) must be
connected to the supply unit with protective ground.
Incorrect connection, incorrect polarity, or inadmissible supply
voltages can damage the gauge.
Reassemble the connection
socket.
Plug in the connection socket.
Secure the connection socket on
the gauge with the screw
(tightening torque ≤0.2 Nm).
Compact FullRangeTM Gauge
VACUUM

BG 5157 BEN / C (2017-07) PKR 261 13
4 Operation
As soon as the required voltage is applied, the measuring signal is available be-
tween pins 2 and 3 (see Appendix B for the relationship between the measuring
signal and the pressure).
Allow for a stabilizing time of approx. 10 min. Once the gauge has been switched
on, permanently leave it on irrespective of the pressure.
The PKR 261 gauge consists of two separate measurement systems (Pirani sys-
tem and cold cathode system according to the inverted magnetron principle). They
are combined in such a way that for the user, they normally behave as one uniform
measurement system.
The optimum measurement configuration for the particular pressure range, in
which measurement is performed, is used:
10-4 hPa
10-2 hPa
1000 hPa
5 × 10-9 hPa
Cold cathode Pirani
•The Pirani measurement circuit is always on.
•The cold cathode measurement circuit is controlled by the Pirani circuit and is
activated only at pressures p < 1×10-2 hPa.
The identification output (pin 1) indicates the current status of the gauge:
Pressure Green lamp on
the gauge
Operating mode Identification
p > 1×10-2 hPa Pirani-only mode 11.1 kΩ(Pirani)
p < 1×10-2 hPa
Pirani-only mode (cold
cathode measurement
circuit not ignited)
11.1 kΩ(Pirani)
Combined operation
9.1 kΩ(combined)
As long as the cold cathode measurement circuit has not yet ignited, the meas-
urement value of the Pirani is output as measuring signal. ("Pirani underrange" is
displayed for pressures p < 5×10-4 hPa).
The measuring signal depends on the type of gas being measured. The curves are
accurate for dry air, N2, O2, and CO. They can be mathematically converted for
other gases (→Appendix C).
If you are using a Pfeiffer Vacuum measurement unit for Pfeiffer Vacuum Compact
Gauges, you can enter a calibration factor to correct the measurement value
displayed (→of that measurement unit).
An ignition delay occurs when cold cathode gauges are switched on. The delay
time increases at low pressures and for clean, degassed gauges it is typically:
10-5 hPa ≈1 second
10-7 hPa ≈20 seconds
5×10-9 hPa ≈2 minutes
The ignition is a statistical process. Already a small amount of depositions on the
inner surfaces can have a strong influence on it.
4.1 Measurement Principle,
Measurement Behavior
Gas type dependence
Ignition delay

14 BG 5157 BEN / C (2017-07) PKR261.oi
As long as the cold cathode measurement circuit has not yet ignited, the measure-
ment value of the Pirani is output as measuring signal ("Pirani underrange" is dis-
played for pressures p < 5×10-4 hPa). The identification output (pin 1) indicates the
Pirani-only mode.
Caution
If the gauge is activated at a pressure p < 3×10-9 hPa, the gauge
cannot recognize whether the cold cathode system has ignited. It
indicates "Pirani-Underrange".
Caution
Once flanged on, permanently leave the PKR 261 gauge in the
operating mode irrespective of the pressure range. Like this, the
ignition delay of the cold cathode measurement circuit is always
negligible (<1 s), and thermal stabilizing effects are minimized.
Gauge failures due to contamination or wear and tear, as well as expendable parts
(e.g. filament), are not covered by the warranty.
Gauge contamination is influenced by the process media used as well as any
existing or new contaminants and their respective partial pressures. Continuous
operation in the range of 10-4 hPa ... 10-2 hPa can cause severe contamination as
well as reduced up-time and maintenance cycles. With constantly low pressures
(< 1×10-6 hPa), the gauge can be operated for more than one year without cleaning
(cleaning the gauge →18).
In general, contamination of the gauge leads to deviations of the measured values:
•In the high pressure range (1×10-3 hPa ... 0.1 hPa), the pressure indication is
too high (contamination of the Pirani element). Readjustment of the Pirani
measurement system →15.
•In the low pressure range (p < 1×10-3 hPa), the pressure indication is usually
too low (as a consequence of the contamination of the cold cathode system). In
case of severe contamination, instabilities can occur (as layers in the meas-
uring chamber peel off). Contamination due to isolating layers can even lead to
a complete failure of the discharge ("Underrange" is displayed).
Contamination can to a certain extent be reduced by:
•geometric protections (e.g. screenings, elbows) against particles that spread
rectilinearly
•mounting the flange of the gauge at a place where the partial pressure of the
pollutants is particularly low.
Special precautions are required for vapors deposited under plasma (e.g. of the
cold cathode measurement system). It may even be necessary to temporarily
switch off the gauge while vapors occur.
Contamination

BG 5157 BEN / C (2017-07) PKR 261 15
5 Maintenance
Gauge failures due to contamination or wear and tear, as well as expendable parts
(e.g. filament), are not covered by the warranty.
DANGER
DANGER: contaminated parts
Contaminated parts can be detrimental to health and enviroment.
Before you begin to work, find out whether any parts are contami-
nated. Adhere to the relevant regulations and take the necessary
precautions when handling contaminated parts.
The gauge is factory-calibrated. Readjusting the gauge can become necessary due
to use under different climatic conditions, aging, or contamination (→14).
The cold cathode measurement circuit, which is dominant for low pressures
(<1×10-3 hPa), is factory-calibrated and cannot be adjusted. By way of contrast, the
Pirani measurement circuit can be adjusted. Any adjustment has a negligible effect
on the pressure range between approx. 10-2 hPa and 102hPa.
•Screw driver 1.5 mm
•Cylindrical pin ø ≈3 mm
Put the gauge into operation (if possible, in the position, in which it will be
used later on).
Evacuate the vacuum system to p << 10-4 hPa, and then wait 10 min.
Turn the nameplate counter-clockwise until the mechanical stop is reached.

Compact FullRangeTM Gauge
VACUUM
While depressing the tactile switch with the
cylindrical pin, adjust the <HV> potentiometer ...
... to 5×10-4 hPa ... or ... to 4.2 V.
Then turn the potentio-
meter counter-clockwise
by ≈120°.
Vent with air or nitrogen to atmospheric pressure and then wait 10 minutes.
5.1 Adjusting the Gauge
Tools required
Procedure

16 BG 5157 BEN / C (2017-07) PKR261.oi
Turn the nameplate clockwise until the mechanical stop is reached.

Compact FullRangeTM Gauge
VACUUM
Adjust the <ATM> potentiometer ...
... to 1×103hPa ... or ... to 8.6 V.
Turn the nameplate back to its original position (it will catch).
DANGER
DANGER: cleaning agents
Cleaning agents can be detrimental to health and environment.
Adhere to the relevant regulations and take the necessary precautions
when handling and disposing of cleaning agents. Consider possible
reactions with the product materials (→8).
Caution
We recommend to replace the Pirani element when cleaning the
gauge.
•Allen wrench AF 1.5
•Allen wrench AF 3
•Open-end wrench AF 6
•Open-end wrench AF 7
•Pliers for circlip
•Polishing cloth (400 grain) or Scotch-Brite
•Tweezers
•Cleaning alcohol
•Mounting tool for ignition aid
•Ignition aid
•Metal seal (11) for anode feedthrough
•Pirani element (13) incl. set of seals (13a, 13b)
5.2 Cleaning the Gauge /
Replacing Parts
Tools / material required

BG 5157 BEN / C (2017-07) PKR 261 17
10
10a
9a
9a
9b
9c
8a 8
11
12
1
2
3
4
7
6
5
13b13a
13
Figure 2:
Remove the gauge from the vacuum system (→21).
Unfasten the hexagon socket set screw (1) on the side of the electronics
unit (2) (→Figure 2).
Remove the electronics unit without twisting it.
Caution
The cover of the electronics unit cannot be removed.
Unfasten the hexagon head screw (3) on the magnet unit (4) and remove
the magnet unit.
Caution
The magnetic force and the tendency to tilt make it more diffi-
cult to separate the magnet unit and the measuring chamber
(7).
Remove the circlip (5) and the polarity insert (6) from the measuring
chamber.
Unfasten the hexagon socket set screw (9c) and remove the insulator (9b)
without twisting it.
Remove the four hexagon socket screws (8) incl. lock washers (8a) on the
back of the measuring chamber.
Carefully remove the following parts in this order (without exerting stress on
the Pirani element (13)): pressure piece (9), anode extension piece (9a),
complete anode (10), metal seal (11) incl. centering ring (12).
5.2.1 Disassembling the Gauge
Procedure

18 BG 5157 BEN / C (2017-07) PKR261.oi
Unfasten the screw fitting (13a) of the Pirani element and remove Pirani ele-
ment together with the copper seal (13b).
The parts can now be cleaned or replaced individually.
Cleaning the measuring chamber and the polarity insert:
Using a polishing cloth rub the inside walls of the measuring chamber and
the polarity insert to a bright finish.
Caution
The sealing surfaces must only be worked concentrically.
Rinse the measuring chamber and the polarity insert with cleaning alcohol.
Allow both to dry.
Cleaning or replacing the anode:
Remove the old ignition aid (10a), for example with tweezers (→Figure 2).
Using a polishing cloth rub the anode pin to a bright finish.
Caution
Do not bend the anode. Do not carry out mechanical work on
the ceramic part.
Rinse the anode with cleaning alcohol.
Allow the anode to dry.
Insert a new ignition aid (10a) into the mounting tool.
Carefully press the anode (clean or new) centered and parallel to the tool
axis into the ignition aid and insert it to a depth of approx. 15 mm. The final
positioning is established after the anode is installed.
Anode
Ignition aid
Mounting tool
5.2.2 Cleaning the Gauge
Procedure

BG 5157 BEN / C (2017-07) PKR 261 19
Slide the screw fitting (13a) and the copper seal (13b) on the tube of the
Pirani element (13) (→Figure 2).
Insert this combination (13, 13a, 13b) into the corresponding conic bore
hole (7) of the measuring chamber.
Tighten the screw fitting (13a) with your fingers while slightly pushing the
Pirani element against the mechanical stop. Then tighten the screw fitting
by one turn with the open-end wrench.
Insert a new metal seal (11) incl. the centering ring (12) centered into the
measuring chamber (7).
Carefully insert the anode (10) with the ignition aid (10a) and extension
piece (9a) slid onto it into the measuring chamber.
Carefully place the pressure piece (9) on the measuring chamber.
Insert the four hexagon socket screws (8) incl. lock washers (8a) and
tighten them uniformly until the mechanical stop is reached.
Carefully slide the insulator (9b) onto the pressure piece (9) and lock it with
the hexagon socket set screw (9c).
Position the ignition aid (10a) by pushing the mounting tool over the anode
pin until the mechanical stop is reached.
Blow the particles in the measuring chamber with dry nitrogen (be careful to
hold the measuring chamber with the flange pointing downwards).
Slide the polarity insert (6) into the measuring chamber until the mechanical
stop is reached.
Place the circlip (5) snugly fitting on the polarity insert.
Caution
Visually check that the anode pin is centered over the middle
hole of the polarity insert (max. eccentricity = 0.5 mm).
If possible perform a leak test (leak rate <10-9 hPa l/s). If necessary slightly
retighten the screw fitting (13a).
WARNING
WARNING: electric arcing
Helium may cause electric arcing with detrimental effects on the
electronics of the product.
Before performing any tightness tests put the product out of
operation and remove the electronics unit.
Mount the magnet unit (4) and lock it with the hexagon head screw (3).
Carefully mount the electronics unit (2). (Make sure the pin of the Pirani ele-
ment is properly plugged into the corresponding hole of the electronics unit.)
5.2.3 Reassembling the Gauge
Procedure

20 BG 5157 BEN / C (2017-07) PKR261.oi
Push the electronics unit up to the mechanical stop and lock it with the
hexagon socket set screw (1).
DANGER
Due to missing ground connection in conjunction with missing
or not correctly tightened hexagon socket set screw (1) danger-
ous contact voltage will occur and electronic components will
be damaged.
Adjust the gauge (→15).
Problem Possible cause Remedy
Measuring signal
continually < 0.5 V
"Error low".
No supply voltage. Turn on the power
supply.
Measuring signal
continually > 9.5 V
"Error high".
Pirani measurement
element defective
(filament rupture).
Replace the Pirani
element (→18).
Electronics unit not cor-
rectly mounted.
Mount the electronics unit
correctly (→19).
The green lamp is ON
and the identification in-
dicates Pirani-only mode
(measuring signal
continually > 4.0 V)
"Pirani underrange".
The cold cathode dis-
charge has not ignited.
Wait until the gas dis-
charge ignites (in case of
contamination with insu-
lation layers, the cold
cathode may completely
fail to ignite). (Cleaning
→18.)
The PKR has only been
activated with
p < 3×10-9 hPa.
Slightly increase the
pressure.
Measuring signal con-
tinually > 5 V or display
> 10-3 hPa although
vacuum pressure is OK.
Pirani measurement cir-
cuit not adjusted, e.g. due
to severe contamination.
Readjust the Pirani
measurement circuit
(→15). If adjustment is
impossible, replace the
Pirani element.
Measurement of heavy
gases.
Convert with the corre-
sponding formula
(→25).
Severe outgassing in the
cold cathode measuring
chamber.
Clean the measuring
chamber.
Measuring signal
unstable.
Gauge contaminated. Clean the gauge.
(Cleaning →18).
5.3 What to do in Case of
Problems