February, 2012
Calibration issues and answers
Service Department
GfG Instrumentation
1194 Oak Valley Drive, Suite 20
Ann Arbor, MI 48108
Ph: +1 734 769 0573
Internet: www.gfg-inc.com
February 2012
Calibration issues and answers
Slide 1
Calibration
• Verify accuracy on a regular
basis to guard against any
unexpected loss of sensitivity
• Document!
February 2012
Calibration issues and answers
Slide 2
Mandatory to use a
"calibrated" instrument
•
USA OSHA 1910.146(c)(5)(ii)(C) “Permit
required confined spaces” requires:
•
Before an employee enters the space,
the internal atmosphere shall be tested,
with a calibrated direct-reading
instrument
•
What does OSHA accept as a
"calibrated" direct reading instrument?
• A testing instrument maintained and
calibrated in accordance with the
manufacturer's recommendations
• The best way for an employer to
verify calibration is through
documentation
February 2012
Calibration issues and answers
Slide 3
Why do instruments need to be
tested and / or calibrated?
•
The response of gas detecting sensors
can change over the life of the sensor
•
The changes may be sudden, or can be
gradual
•
Substances or conditions present in the
atmosphere can have an adverse effect
on the sensors
•
Different types of sensors have
different constraints and conditions
which can lead to loss of sensitivity or
failure
•
Important to know how sensors detect
gas to understand conditions that can
lead to inaccurate readings
February 2012
Calibration issues and answers
Slide 4
Make sure the instrument
has been calibrated!
• Follow manufacturer
recommendations
• “Zero” instrument in fresh air prior
to use
• Verify Accuracy Daily!
• Functional “bump” test sufficient
• Adjust “span” only if necessary
February 2012
Calibration issues and answers
Slide 5
Loss of sensitivity
can be due to:
• Aging or desiccation of the sensors,
• Mechanical damage due to dropping or
immersion
• Exposure to sensor poisons present in
the atmosphere being monitored
• Loss of sensitivity due to other causes
February 2012
Calibration issues and answers
Slide 6
Regulatory
Requirements
• OSHA 1910.146 requires use of a
“calibrated” instrument
• This means (per OSHA CPL 2.100) that
the instrument must be maintained and
calibrated according to manufacturer
guidelines
February 2012
Calibration issues and answers
Slide 7
Manufacturer Guidelines
• OSHA holds instrument
users accountable to
maintain, calibrate and
operate their
instruments according
to manufacturer
guidelines
February 2012
Calibration issues and answers
Slide 8
Additional Canadian
Requirements
•
Canadian Standard CSA 22.2 requires mandatory “bump
test” before each day’s use for all instruments equipped
with a sensor for the measurement of combustible gas
•
Operation manuals of instruments Certified for sale in
Canada carry this warning
Small “c” indicates the
certification includes
conformity with
Canadian requirements
00000000000
February 2012
Calibration issues and answers
Slide 9
Calibration Frequency
• The safest course of action is to
expose the sensors to known
concentration test gas before
each day’s use!
• This test is very simple and
takes only a few seconds to
accomplish
February 2012
Calibration issues and answers
Slide 10
Functional “Bump”
Test vs. Calibration
• Functional “bump” test only
provides verification of sensor
performance
• Calibration includes adjustment
• Only necessary to adjust
sensor sensitivity if readings
are off
• Most manufacturers
recommend adjustment if
readings are off by more than
10% of expected values
February 2012
Calibration issues and answers
Slide 11
Industrial Safety Equipment
Association (ISEA) Guidelines
• Provides procedure for lengthening
the interval between calibration
checks
• During period of initial use of at
least 10 days in the intended
atmosphere, check the response
daily to be sure there is nothing
in the atmosphere which is
poisoning the sensor(s).
• Period of initial use must be of
sufficient duration to ensure that
the sensors are exposed to all
conditions which might have an
adverse effect on the sensors.
February 2012
Calibration issues and answers
Slide 12
Industrial Safety Equipment
Association (ISEA) Guidelines
• If these tests demonstrate that it is not
necessary to make adjustments, the
time between checks may be
lengthened
• This interval should not be lengthened
beyond thirty days
• History of the instrument should be
tracked or logged
February 2012
Calibration issues and answers
Slide 13
Industrial Safety Equipment
Association (ISEA) guidelines
• Any conditions, incidents, or
exposure to contaminants which
might have an adverse effect on the
sensors should trigger immediate
re-verification before further use
• Any changes in the work being
done, or environment in which the
instrument is being used should
trigger re-verification by means of
daily checking that it is safe to
lengthen the interval between
calibration checks
February 2012
Calibration issues and answers
Slide 14
Conditions which should trigger
immediate re-verification of calibration
• If there is any doubt at any
time as to the accuracy of the
sensors, verify the calibration
of the sensors by exposing
them to known concentration
test gas before further use!
February 2012
Calibration issues and answers
Slide 15
Don’t be afraid of calibration!
• Modern designs make calibration
easy and automatic
• Keep the Calibration Materials
With the Instrument!
• All-In-One Calibration Mixtures
Make Functional Testing Easy!
February 2012
Calibration issues and answers
Slide 16
Is the concentration of gas used to
calibrate instruments dangerous?
Not at all!
Consider the concentration
if you leaked an entire
cylinder of CO cal gas
into the interior space of
a typical passenger van
Approximate interior volume
of Honda Odyssey EX-L =
300 cubic feet
Typical cal gas cylinder
holds 34 liters = 1.2 cubic
feet @ 50 ppm CO
1.2 cubic feet = 0.4% of the
volume of the entire
vehicle
50 ppm X .004 =
concentration in vehicle =
0.2 ppm CO
February 2012
Calibration issues and answers
Slide 17
What about a cylinder that
contains 25 ppm H2S?
34 liters = 1.2 cubic feet
@ 25 ppm H2S
10 X 10 X 10 room =
1,000 cubic feet
1.2 cubic feet = 0.12% of
the volume of the
entire room
25 ppm X .0012 =
concentration in room
= 0.03 ppm H2S
February 2012
Calibration issues and answers
Slide 18
Record
Keeping
• Documentation is critical!
• Without good records you
cannot defend or explain
your procedures
• If you don’t have the
records to prove it was
being done right -- it wasn’t!
February 2012
Calibration issues and answers
Slide 19
Atmospheric hazards are frequently
invisible to human senses
• You don’t know whether it’s safe until it’s been tested!
February 2012
Calibration issues and answers
Slide 20
Bump Test (Manual Procedure)
•
Make sure the instrument is located in fresh air,
turn on, and allow to warm up
•
Note readings, and perform fresh air zero if
necessary
•
Attach calibration adapter; instrument will
display "AutoCal menu"
•
Press "Exit" to show normal gas reading
screen
•
Flow gas to sensors; alarms should activate,
and readings should stabilize at expected
values (if sensors fail to respond
properly, instrument should be
calibrated before further use)
•
Turn off gas, remove cal
adapter and allow readings
to stabilize at fresh air
values
February 2012
Calibration issues and answers
Slide 21
Bump Test
•
Response of
sensors to Quad
Mix (graphs)
•
Readings
recorded while
instrument
operated in
normal gas
reading mode
•
Simultaneous
response to all
four gases, as
well as match
between cal gas
concentrations
and readings
February 2012
Calibration issues and answers
Slide 22
Bump Test
•
Response of
sensors to Quad
Mix (table)
•
Readings
recorded while
instrument
operated in
normal gas
reading mode
•
When a sensor
is in alarm
readings are
recorded in red
February 2012
Calibration issues and answers
Slide 23
AutoCal
• AutoCal allows instrument to be “Fresh air” or
“Calibration” (span) adjusted if needed
February 2012
Calibration issues and answers
Slide 24
Attach Cal Cap to Enter Fresh
Air and Span “AutoCal”
Attach cal cap to unit;
instrument automatically
enters “AutoCal “ menu
Choose ZERO or
CAL and apply
gas
(if calibrating),
e.g. an H2S/CO
mix.
Adjustment is
automatic
Display shows
when cal adjust
has been
successfully
completed
February 2012
Calibration issues and answers
Slide 25
Can also enter “AutoCal” mode by pushing
“Reset” and “Zoom” buttons at same time
Push “Reset” and “Zoom”
at same time; instrument
automatically enters same
“AutoCal “ menu
Choose ZERO or
CAL and apply
gas
(if calibrating),
e.g. an H2S/CO
mix.
Adjustment is
automatic
Push at same time to
enter “AutoCal” Mode
February 2012
Display shows
when cal adjust
has been
successfully
completed
Calibration issues and answers
Slide 26
Calibration gas concentrations
•
Best to use the default cal gas
concentrations
•
Default GfG concentrations used to
calibrate instrument:
• 200 ppm CO
• 20 ppm H2S
• 50% LEL methane (CH4)
•
If you use different concentrations you
must change instrument settings!
February 2012
Calibration issues and answers
Slide 27
How does the accuracy of the cal gas affect
the accuracy of the readings?
•
Standard GfG Quad Mix cal gas has 25 ppm
H2S, 200 ppm CO, 50% LEL CH4; +/- 10%
accuracy, w/ 12-months shelf life dating
•
GfG Quad Mix also available with +/- 3%
accuracy, w/ 6-months shelf life dating
•
Accuracy of sensors = +/- 5% of reading
•
Using +/- 3% accuracy gas means the
accuracy statement for the combined
instrument and cal gas system becomes +/8% of reading, or the minimum resolution of
sensor, whichever is greater
February 2012
Calibration issues and answers
Slide 28
Range and resolution of GfG
instruments used to detect H2S
•
Standard full range is 0 – 100 ppm. (Users
can optionally choose a 0 – 500 ppm extended
full range version of the product.)
•
Standard setup displays readings in 0.2 ppm
steps over the 0 – 1.0 ppm range.
•
From 1.0 – 99.9 ppm measurements are
always incremented in 0.1 ppm steps.
February 2012
Calibration issues and answers
Slide 29
Effect of ± 5% sensor
accuracy on readings
At 1.0 ppm actual, reading
between 1.05 and 0.9 ppm,
so accuracy becomes +/minimum resolution = +/0.2 ppm
0
February 2012
5
10
15
25
Calibration issues and answers
Slide 30
30
Effect of calibration gas (± 3%) and sensor accuracy
(±5) on readings: combined effects = ±8%
At 1.0 ppm actual, reading
between 1.08 and 0.92
ppm, so accuracy becomes
+/- minimum resolution =
+/- 0.2 ppm
0
February 2012
5
10
Calibration issues and answers
15
Slide 31
25
30
So how accurate are the readings?
•
Thus, on a standard basis, from 0 – 4 ppm the
accuracy is +/- 0.2 ppm; from 4.0 to 100 ppm the
accuracy is +/- 5% of reading.
•
If you choose the 0.1 ppm resolution over the 0 –
1.0 ppm range, from 0 – 2.0 ppm the accuracy is
+/- 0.1 ppm, from 2.0 to 100 ppm the accuracy is
+/- 5% of reading
February 2012
Calibration issues and answers
Slide 32
Use DS400 Docking Station for daily bump
check and / or periodic calibration
February 2012
Calibration issues and answers

Standalone operation:

No PC required

Automatic bump-test

Automatic span
calibration

Success / failure
indication after each test

Economic use of test
gas

Easy collection of unit
test and logged data

Reduced maintenance
cost
Slide 33
Use TS-400 Test Station
for daily bump check

Standalone operation - No PC required!

Automatic bump-test only

Success / failure indication after each test

Economic use of test gas

Easy collection of unit test and logged data
February 2012
Calibration issues and answers
Slide 34
Comprehensive
Test Reports

Easy to generate custom test
reports
February 2012
Calibration issues and answers
Slide 35
Automatically generate calibration and
bump test certificates
February 2012
Calibration issues and answers
Slide 36
DS-400 Docking Station for daily bump
check and / or periodic calibration
• Standalone operation:
• No computer required!
• Docking station controlled by
instrument’s control buttons:
• Push "Test" for Bump Test
• Push "Cal" for Auto Cal
• Push "Cancel" to charge only
February 2012
Calibration issues and answers
Slide 37
DS-404 Multi-inlet Docking Station for
bump check and periodic calibration
• Inlets for 4 cylinders of gas
• Automatic Bump and Cal for 5, 6 and 7
channel instruments
• Supports:
• Quad mix (O2, LEL, CO, H2S)
• 5-mix with SO2
• 5-mix with CO2
• Isobutylene
• HCN
• NO2
• And other individual gases
February 2012
Calibration issues and answers
Slide 38
Using DS400 Docking Station for daily bump
check and / or periodic calibration
February 2012
Calibration issues and answers
Slide 39

Standalone
operation: DS-400
does not require
connection to an
external computer

Test results and other
messages displayed
on instrument LCD
Using DS-400 Docking Station for daily bump
check and / or periodic calibration
• Using DS-400 allows
instrument to record
"Bump Test" as specific
event in instrument's
memory
• It is possible to set a
"Bump Test Due" date in
the instrument's memory
• Only way to reset next
"Bump Test Due" date is
by means of DS-400
Docking Station
February 2012
Calibration issues and answers
Slide 40
Using DS-400 Docking Station for daily bump
check and / or periodic calibration
•
Make sure DS-400 attached to test gas and power
•
Make sure the instrument is located in fresh air,
turn on, and allow to warm up
•
Note instrument readings, and perform fresh air
zero if necessary
•
Place instrument in DS-400
•
Docking station controlled by instrument’s
control buttons:
• Push "Test" for Bump Test
• Push "Cal" for Auto Cal
• Push "Cancel" to charge only
February 2012
Calibration issues and answers
Slide 41
How to do bump test
•
Make sure instrument turned on
• Best if instrument allowed
to warm-up at least 5
minutes before bump test
•
Make sure Docking Station
plugged in and connected to
gas
• Higher inlet is for fresh air
• Lower inlet is for span gas
•
Place G460 in Docking Station
•
Instrument display will indicate
status and results of test
February 2012
Calibration issues and answers
Slide 42
How to do bump test
• After 10 second count-down; Docking
Station automatically performs bump test
• Instrument screen shows a check mark
besides each sensor as bump check
completed
• If G460 is not removed from Docking
Station; 5 minutes after test completed
G450 turns off and goes into charging
mode
February 2012
Calibration issues and answers
Slide 43
DS400 Docking Station



Bump-Test includes:

Visual alarm function

Audible alarm function

Time for activation to alarm 1

Time for activationto alarm 2

Time to t50
Calibration Test Includes:

Fresh air zero adjustment

Span calibration adjustment
All test results:

Stored to instrument memory

Stored to flash memory card in Docking
Station
February 2012
Calibration issues and answers
Slide 44
What to do if G460
fails bump test
• Red color warning screen and message
indicates bump test failed
• This means G460 needs to be “Autocal”
adjusted before further use
• Remove instrument from Dock, and press
“Reset” (center) G460 control button to
clear alarm message
• Place G460 back in Dock
• Before end of count down press Autocal
button
February 2012
Calibration issues and answers
Slide 45
Questions?
February 2012
Calibration issues and answers
Slide 46