Mass SpectrometryFault finding and trouble shooting

Or: Giving the bullet to those pesky faults

Disclaimer

3000 volts can kill

Protect your eyes

230 Volts can kill

Mass spectrometers can cause pain

Mental pain!

Please beware that any work on the instrumentis carried out at your own risk. Isomass Scientific cannot be held responsible for injury or damage caused by following these techniques.

Hot solderingirons can burn

Salesman’s view of solving instrument problems

New!

Reality

• Budget shortfalls– Not enough money to buy a new instrument– Not enough money to pay for service

What to do• Learn how to look after your own instrument– Go on the manufactures training courses– Ask questions during the installation and any visit

made by an engineer– Regularly attend ASITA– Read the manual and other books– Take an electronics course

Fault Finding• Use the instrument supplier as a resource– The engineers are trained on the instrument– The engineers want to help– The engineers will have access to more

information• Take your time– Fault finding is not a race– More intervention usually leads to more damage– Take notes and pictures

Fault Finding• Beware of dangerous voltages that might be present

in the unit under investigation– The 230 volt supply into most units can be fatal if touched– Source supplies are usually at high voltage, > 3kv

• Be careful when connecting or disconnecting meter probes– A badly placed probe can cause a short and further

damage• Double check connections and meter setting before

turning on the unit under test

Fault Finding

• Check power supplies first– Fuses, check with a meter on resistance not just

visually– If a supply voltage is less than expected it could be

that the supply is damaged or the load is pulling the supply voltage down

– Regulated supplies should have very low a.c. ripple– All electronics can be seen as either a supply or

load

Fault FindingThink before acting #1

5 minutes thought can save hours of work

Fault FindingThink before acting #2

Think about the problem before acting

Art is a science• Learn to draw– Draw a block diagram of the fault area– Write down the inputs and outputs of each block– Make a list of possible causes

My block diagram

Power Block Diagram

A few simple techniques

• Swap– Exchange the suspected part

• Measure– Compared the measured parameter with the

expected value• Observe– Look to see what’s happening

• Write– Keep good notes

Swap

Pirani reads 1e-3mbar

Pirani reads atmosphere

Simplify

Pirani showingatmosphere after

10 minutes pumping

Use a blank at point 'A' totest the sub- system withinthe instrument as a whole

Voltage Measurement

Voltage Measurement

• Multimeter set to a.c. or d.c. voltage as required– Black lead in common socket– Red lead in V socket

• Voltage measured across one component measures across all components in parallel– Voltage is measured in parallel– Circuit is powered

• Connect red probe to one lead of the component and the black probe to the second lead– If meter is auto-ranging note the displayed multiplier

Current Measurement

Current Measurement• Multimeter set to a.c. or d.c. current as required

– Black lead in common socket– Red lead in mA or A socket as required, if in doubt start in A

socket• Multimeter must be in series with the component

– If necessary unsolder one lead from the board– Circuit is powered

• Connect red probe to the lead of the component and the black probe to the point the lead was previously connected to– If meter is auto-ranging note the displayed multiplier

• Often easier to measure voltage across a resister and use V=IR

Resistance Measurement

Resistance Measurement

• Multimeter set to resistance– Black lead in common socket– Red lead in Ω socket

• Component must be measured in isolation– Circuit is not powered– If necessary unsolder one lead from the board

• Connect red probe to one lead of the resistor and the black probe to the other lead– If meter is auto-ranging note the displayed multiplier

Start with the obvious

If a light does not work....

Check the light bulb before dismantling thelight switch, changing the fuse in the basement etc.

Start with the obvious

Two bulbs might have blown but it's more likely that there is a fault common to both e.g. the fuse in the basement

If two light bulbs do not work....

Fault FindingTake good, clear notes when the instrument is working correctly

and notes during any fault finding procedure

Don't forget, "RTFM" !

Power Control

230 Volts

Switched outletRelayControl

Vacuum control

Vacuum parts

Vacuum Start-up

Quick Rotary Pump Test

Penning Gauge

Turbo Pump Faults

Vacuum Service

• Rotary pump– Change the pump oil every 6 months

• Turbo pump– Change the oil wicks yearly

Ion Source Control

Ion Source Electronics

~4A ~700µA~800µA

1.5mA

~4.2A

Ion source

Exploded Ion Source

Source Cleaning

Magnet Supply

Magnet Screwdriver Test

Inlets

Dual Inlet Valve Control

GC Combustion

EA

GasBench

GasBench

#140, 5700 – 1 Street S.W.,Calgary, Alberta T2H 3A9isomass@isomass.com

Tel: (403) 255-6631 . Fax: (403) 255-6958Toll Free: 1-800-363-7823