Designing Automated Test System For Power Supply Testing
Having a hard time designing your tester?
Designing and conceptualizing an ATE is not an easy task.
Here are some points and steps you may consider in designing your own automated test equipment (ATE) that will fit your needs.
List down all the existing power supply, newly develop power supply and the future projects with the following needed information:
o Input Power requirement: for input source, you have to plan what input source you may need to cover all input requirement for all the your product lines.
o Output power requirement: number of loads you need to consider, this will range from the high power range to low power range.
o Number of outputs and signals: this is very critical since you have to plan for the standard mux allocation. For this, more mux allocation the better.
o Control switches: review each test requirement for each of the product for all the test that requires relay or switches. You have to be very careful in planning this out. This will be use on how many general purpose switches or relay you will install in your ATE. You can check also new test methodology that might be possible test for the new products.
From the list, you should accomplish the following information:
o You will have an idea on what input source your going to use to cover all power supply you’re about to test.
o You will have an idea on how many load modules you need to install to cover high power multiple outputs power supplies. You will also need to add low current load module for lower current outputs.
o You will have idea on how many muxes and switches your going to use.
Test Interface Panel
You need to consider the test interface your going to use for your ATE. There are a lot of choices in the market.
For test panel connector, you have to consider the following:
o Quality of contacts, good contact probes to eliminate contact resistance that will affect your measurements.
o Flexibility, easy to plug in, easy to unplug, quick disconnect, low insertion and extraction force needed.
o Serviceability, easy to replace. You have to consider also on the connector that is easy to replace and
o Contact life cycle, you have to consider long life cycle connector otherwise you have to change it frequently.
You need to consider the following points for selecting an equipment.
o Availability of equipment – make sure that you will have a permanent equipment for your ATE.
Since the equipment will be fixed on your ATE, make sure that the equipment will not be shared with other test setup.
o Communication interface of the equipment, usually all equipment have GPIB (general purpose interface bus) for remote control.
o You have to consider also that in building ATE, this will be a standard test setup. You might build more ATE using same configuration from equipment to software. In this regard, you have to consider an equipment that still available in the market just in case you need to build more ATE.
o Serviceability, consider an equipment that technical support from the manufacturer is still available.
o Easy to install on your ATE Rack, usually, test equipment are in standard sizes, usually its 19″ wide which will fit on the 19″ rack.
Use appropriate cables for your ATE.
o Load Cables: use rated cables that can handle rated maximum current of each module. Make sure that you have to consider only 80% of the cable ampacity.
o Sense cable for voltage sensing to you DVM: use a twisted stranded wire for your sensing to your DVM.
o Sense cable for the Oscilloscope: use shielded coax cable, scope probes.
o Input cables for input:
For AC, Make sure that you will check the rated ampacity of the cable. Make sure that the ground is connected as well. Use twisted stranded thin cable for the sense.
For DC, Make sure that you will check the rated ampacity of the cable. Use twisted stranded thin cable for the sense.
o Input cables for equipment input: always connect the ground of each equipment to the main input ground.
o GPIB Cables for remote programming
Here’s the common ATE test equipment setup
o Oscilloscope (4 channel)
o DVM (6.5 digit resolution)
o Differential Probes for Input
o Switch Control
– 10 muxes (or more)
– 10 general purpose relays (or more)
– 10 DIN
– 10 Douts
o Electronic Loads:
– 16 – 300W load
– 2 – 150W load or lower wattage load module
o Input Source
– 6.5KVA Ac Source
– 2KW DC Source (parallelable with additional source)
o Power Meter
o Auxiliary Sources
– 12VDC stand by supply
– 5VDC stand by supply
o I2C Interface
o Computer with GPIB interface for the equipment and a USB or serial interface for the i2c controller.
o Power Bars or Power distribution unit for equipment input supply.
Assembling your ATE
o Rack assembly: If you are planning to use a two rack system to accommodate all the equipment for your ATE, connect the two rack together with a bolt and nut, remove the cover in the middle of the rack for easy access on both racks.
o Install all the mounting brackets of each equipment
o Mounting the equipment: Use equipment railings in installing your equipment. Usually, the assignment of each equipment matters on wiring process. For my opinion, I put all the equipment connected on the secondary side of the power supply on the left side (if you are facing the rack).
o Left side of the rack: This equipment will be connected on the secondary side of the UUT.
– DVMs or Data Acquisition
– Switch control
– Electronic loads
o Right Side of the rack: This equipment serves as a source to the UUT.
– Input Source
– Axillary sources
– Power Meter
o Screw all equipment’s mounting bracket to the rack.
Note: Record all the rail assignment for your documentation purposes.
Wiring your ATE
Wiring and ATE is very critical, and it will greatly affect your measurements.
Here’s some steps and pointers you might need to consider in wiring your ATE.
o Wire first the equipment input. Make sure that the input cables for the equipment is in one side of the rack (leftmost side if your facing at the back of the equipment). Harness properly using a cable tie or velcro.
o Connect GPIB cables on all the equipment. Start connecting from the oscilloscope down to the
electronic loads then to the input source to the computer. Harness the GPIB cables same on where the ac input cables of the equipment located.
o Prepare the load cables, make sure that it is long enough that reach the test interface panel. Label the load cable from load1 to load 18, both positive (red) and negative (blk) cables at both ends. Connect all the load cables to the load, double check the cable rating that would match the load module rating. Load cable rating should be above by 20% on the maximum load module maximum current. If your not taking any measurement from the load, you don’t need to wire a sense cable, just set the module to local sensing. Harness the load cable separately with the equipment input cables. Harness it on the other side of the rack.
o Prepare the sense cables, make sure that it is long enough to reach the test interface panel. Label each sense cable for each mux assignment on both ends. Harness the cables from the switch control unit / DVM to the test interface panel. Harness the sense cables together with the load cables.
o Prepare the sense shielded cables, make sure that it is long enough to reach the test interface panel.
Label each sense cable for each mux assignment on both ends. Harness the cables from the switch control unit / oscilloscope to the test interface panel. Harness the sense cables together with the load cables.
o Wiring the input source. AC input source output should be wired through the power meter. DC Input source will be wired directly to the test interface panel. Measurement for the DC input source will be taken from the source itself. Both AC and DC Input source should use a remote sensing scheme to eliminate the voltage drop. Harness the input source cables separately.
o Wiring the auxiliary sources, make sure that the cables will reach to the test interface panel.Harness these cables together with the input source.
GPIB equipment Addresses
You have to assign a standard equipment GPIB address for each of the equipment.
Valid GPIB address is from 1 to 30. Usually, the default manufacturer’s GPIB address is used unless otherwise it has a conflict.
Here are the names other professional called an ATE
o ATE – Automated Test Equipment
o ATS – Automated Test Systems
o Power Test
o Auto Test
o Mixed Mode Tester
o FT – Functional Tester
o CT – Computer Test