Electronics Trouble-Shooting Secret Weapon

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The other day I was working on a particularly difficult electronics problem with an ion gun controller and to help figure it out, I needed to dust off my trusty Huntron Tracker. I don’t need to use it very often, but when needed, there is nothing better for troubleshooting electronics problems.

Huntron Tracker
Huntron Tracker

First introduced in 1979, the Huntron Tracker displays an analog signature, which is a combination of resistive, capacitive, inductive, and semi-conductive characteristics. This visual display is very helpful for comparing electronics components on a defective board. The Tracker is particularly useful for comparing components on a known defective electronics board with a known good one. The Tracker applies a tiny AC voltage to the probes so you can test components with no power applied to the board that you are testing.

Compare known good board components to defective board components
Compare known good board to defective board

You can usually find defective electronics components with a DVM (digital volt meter) by testing diodes and capacitors, then measuring resistance values. But there are times when all of the individual components check out as OK with a DVM, but you know that there must be at least one defective component because the board does not work properly. For those times, the Huntron Tracker works like a champ every time. By finding some components that read differently with the Tracker, you can get a clue and ultimately, find the problem. 

The early model Huntron Trackers had a little CRT display and three power level settings. Those models are still available on EBay for about $300.00. The Tracker that I use is one of these early ones and it still works well.

Over the years Huntron Trackers have evolved and today’s models include more power settings, automated testing, and software. For more info visit Huntron at –

https://huntron.com/products/tracker28s.htm

If a new Huntron Tracker is out of your price range or you can’t find an older one, there are also inexpensive curve tracer kits available on eBay that provide Tracker functionality using an oscilloscope. To find those, go to eBay and search for Curve Tracer kit.

Curve tracer board

Programming the 9103 With Python – Part 1: Standard Speed

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New sample Python code for the 9103 is now available on RBD’s website. The 9103’s API is easy to program with any language and documented fully, but as always with any device programming, a few examples always help. We chose Python because it’s well supported, easy to understand even if you’re using another language and compatible with a number of popular lab control and analysis environments.

The sample code we provide is open-source and free for you to use and distribute as you see fit.

(If you haven’t taken a look at the 9103 USB auto-ranging picoammeter, everything you need to know can be found here. Measure bi-polar DC current from picoamps to milliamps, with optional built-in bias and 5 kV isolation.)

Programming the 9103 with Python

A Quick Look at the Standard Speed Sampling Code

Python’s pySerial module abstracts the calls to class-compliant USB serial COM port drivers, so setting up communications with the 9103 is a matter of a few simple calls:

port=serial.Serial(
    'com' + port_number,
    baudrate=57600,
    bytesize=serial.EIGHTBITS,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    xonxoff=False,
    timeout=1)

With the addition of a few helper functions for handling ASCII, it’s simple to write functions to send individual commands to the 9103. The following sets the auto-range and filter settings:

def message(message_string):
return bytes('&'+ message_string + '\n','utf-8')

def command_range_auto():
port.write(message('R0')) # put in autorange

def command_default_filter_32():
port.write(message('F032'))

Similarly, with the addition of a few helper functions, the 9103 samples can be read with a simple loop that reads lines from the port buffer: In this case, we’ve setup the 9103 to read in interval mode, and poll the port for incoming samples, with a simple keyboard interrupt. This code also writes the sample information to a text file.

try:
while True:
msg=port.readline().decode('utf-8').rstrip()
print(msg)
parsed = parse_message_for_sample(msg)
if parsed:
samplefile.write( parsed + '\n')

except KeyboardInterrupt:
pass

All of the code is commented and documented in the Python file.

Using Python with LabView and MATLAB

The Python code samples can be helpful to both LabView and MATLAB users.
LabVIEW now supports Python through the Python Node, which features low-latency calls from a LabVIEW Block Diagram using LabVIEW primitives.

The MATLAB Engine API for Python allows you to call MATLAB as a computational engine from Python, and you can call functions and objects in Python from MATLAB.

More to Come…

Next up we’ll be posting some sample code to write and read using the high-speed version of the 9103. Since high-speed data from the 9103 arrives in packets, there are some minor differences in parsing the message samples.

Research Gases for Laboratories

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Laboratory gases are readily available in large cylinders from companies such as Airgas, Norco and local welding supply companies.

Large gas cylinders

But for small quantities of gases or specialty gases used in vacuum optics such as UV sources and Ion guns, it may make more fiscal sense to use lecture bottles instead of the larger size gas cylinders which are commonly found in laboratories.

Lecture bottles are small compressed gas cylinders that are typically 12-18 inches long and 2 to 3 inches in diameter.  

Lecture Bottle

They hold approximately 2 cubic feet of gas and are pressurized to as much as 1800 PSI.   High pressure gas cylinders require a regulator to step the pressure down.  The pressure required for the application will determine which regulator is needed.   For example, the Varian variable leak valve used on many 04-303 ion sources can take a maximum pressure of 500 PSI.  However, it is recommended that the argon gas pressure be set to 15 to 25 PSI for best results.    

Since lecture bottles are small, it costs less to ship them.  But most importantly, when you buy a lecture bottle you are buying the bottle as well as the gas.  Full sized cylinders are generally rented for a monthly fee in addition to the cost of the gas and delivery. Factoring in the monthly rental fee for the cylinder, a lecture bottle could be much less expensive over time. Especially for optics like UV sources where you may only use it a few times a year.

In the US, Matheson provides a wide assortment of specialty gases in lecture bottles.  Matheson also has a worldwide distribution network.

https://www.mathesongas.com/gases

Ultra-high purity gases have 5 nines (99.999%) purity and Research grade gases have 6 nines (99.9999%) purity.   

Another provider in the US that carries Lecture bottles is Advanced Specialty Gases –

https://www.advancedspecialtygases.com/PureGas.html

In Europe,  Messer can provide gases in small cylinders:

https://www.messergroup.com/

https://www.messer.de/spezialgase

In the UK, CK Gas Products provides a variety of gases in lecture bottles:

http://www.ckgas.com/lecture-bottles/

Gas regulators are available from these companies as well as from Grainger. Be sure to specify the type of connection on the gas bottle when you order it and also to order the correct connection on the regulator. For best results, insert a valve between the regular and the outlet line. Finally, you also will need to pump out the line and regulator before opening the gas bottle as otherwise your gas will become contaminated with air.