FAQ AMS Hardware

This is a list of Frequently Asked Questions (FAQs) about Aerodyne Aerosol Mass Spectrometer (AMS) hardware. The initial list is based on the presentation by Ed Fortner and Bill Brooks of Aerodyne (with input from Wade Robinson and John Jayne) at the 10th AMS Users Meeting in Toronto, Canada. Anyone from the AMS Community is welcome to add to the questions and answers. If you don't have a Wiki account yet, you can request one by clicking here.

Recommended AMS Maintenance

• Clean fan filters on all electronic components and Turbo Pump fans
• Check and tighten 80/20 (frame) fasteners after shipping
• Clean the instrument, particularly the raw aluminum chamber surface. Avoid exposure to elements, especially sea salt.
• Computer Hard Drive maintenance
• Always keep the vacuum system operational, Don’t leave instrument in the powered down state for extended periods (> 1-2 weeks).

Frequently Asked Questions

What are the operating currents for all pumps?

Pump Number	Gas Load Off (mA)	Gas Load On (mA)	Delta T(C) (Closed) (&)	Delta T(C) (Open) (&)
P2	450	850	9	13.3
P3	250	300	9	9.3
P4	200	250	6	6
P5	< 200	< 200	6.2	6.5
P5	~200	~200	9.6	9.6

(&) Delta T = Pump Temp – Ambient Temp

What are your backing pump pressure and lens pressure?

Answer: you can read both of them with the same 10 Torr Baratron pressure gage (displayed in the electronics box). There is a 3-way valve, when pointing up if reads the lens P, when pointing down in reads the backing pump P.

If one turbo pump fails can I keep running the system?

Answer: NO !!! This may kill several other pumps (and that has actually happened to at least one group).

When should I align the lens?

Answer: After shipping or if there is reason to believe that the instrument has been bumped.

When can I turn on the MCP after venting?

A: It depends. It is always best to pump overnight, but if the system has only been vented an hour or two, and there is a need to collect data right away then after about 1/1.5 hours.

When can I turn on the filaments after venting?

A: About 45 minutes.

Why is my flow rate so high?

A: The key here is that the AMS does not measure a flow. It is measuring the pressure and a calculation is done in software to give the flow rate. So if you are measuring the backing pump pressure then you will have a flow rate which will be much higher than expected. Simply turn the valve on the front of the AMS to measure the lens pressure and your flow rate will be correct.

How much information does Aerodyne need to help me diagnose my problem?

A: as much as possible. E.g. we often get questions such as "The AB is low, what should I do?". It is impossible to know what the cause his without knowing many additional pieces of information, such as your flow rate, state of pumping system, MCP voltage, single ion measurement, etc.

At which point where different updates to the AMS electronics introduced?

• Chopper circuit upgrade: New 14 pin connector, not back compatible (starting with instrument 215-073)
• HB display is now real (Rev L 215-077)
• Improved 24V amperage reading on Pump Box (215-085)
• New pump controller firmware features:
  • Master Interlock > V4.1 (215-070)
  • Selective pump on/off control

I don't have a PToF Airbeam after I shipped the instrument, what's the problem?

• This problem is often caused by the timer card being unseated during transport. The fix to try is to shut down the computer, open it, take the timer card out and put it back in (making sure it is well-seated in the PCI slot) and trying again.

My chopper servo is not moving, what to do?

• Question: we're having with the chopper servo (it doesn't move). We tried swapping in a new servo motor with no effect, making me think that the problem is with the chopper board itself. The chopper still spins, and we found pins in the chopper cable carrying 12V and ~3.7V, which I think are the chopper and servo power, respectively. None of the cable pins showed a voltmeter response to changing the servo position through the software (DAQ or CRITR), though I'm not sure how/where to measure this.

• Reply: it sounds like you are missing the PWM signal that positions the servo. This is the yellow wire on the servo. The red wire is the 3.7V that you measured and black is ground. The PWM signal originates from the 6024 NI card, usually CTR0 routed to USER1 or USER2 BNC, the small jumper wire on the BNC2090 i/o panel. I would try connecting the appropriate USER BNC to a scope and use CRITR to vary the signal. You should see a variable width (1-2 ms) repeating at 50 Hz. If you don't see this there is something wrong with the NI card.