Resistance Measurements
The System provides the ability to measure from 0W up to 19MW using various techniques to optimize the measurement effectiveness. You can choose between using a constant-current source (0.1µA to 10mA), a DC constant-voltage source (.02V to 2V full range), or AC complex-impedance measurements over the range of 100Hz - 1KHz. Resistance tests can be used with external sense (4-wire Kelvin measurements), and in conjunction with multi-point guarding to isolate individual components. Guard currents up to 100mA are available. Up to 16 distinct measurement and stimulus functions can be active during a single measurement.
Capacitance Measurements
The System provides the ability to measure from a few pF up to 20,000µF. You can choose between using a constant-current pulsed source (1mA to 10mA), or AC complex-impedance measurements over the range of 100Hz – 100KHz. Capacitance tests can be used with external sense (4-wire Kelvin measurements), and in conjunction with multi-point guarding to isolate individual components. Guard currents up to 100mA are available. Up to 16 distinct measurement and stimulus functions can be active during a single measurement.
Inductance Measurements
The System provides the ability to measure from a few µH up to 1000H. Measurements are made by using complex-impedance measurements with stimulus frequencies between 100Hz and 100KHz and full-range amplitudes of .02V to 2V. Inductance tests can be used with external sense (4-wire Kelvin measurements), and in conjunction with multi-point guarding to isolate individual components. Guard currents up to 100mA are available. Up to 16 distinct measurement and stimulus functions can be active during a single measurement.
Voltage Measurements
For UUTs that have batteries, DC amplitudes up to 10 volts can be measured. Fully differential measurements can be made up to ±8V from chassis ground.
Transistors
Transistors can be tested as two diode junctions, or tested for Beta while in-circuit. The Beta test can help determine proper insertion polarity for transistors that can be installed backwards, but with the base still in the middle. This type of fault can not typically be detected with diode testing of the junctions.
FETs
FETs can be tested for turn-on voltage. By sweeping a voltage into the gate while monitoring the Source/Drain impedance, the FET can be checked for proper orientation and operation.
Opto-Isolators
Opto-isolators can be tested by sourcing into the input leads while measuring the output impedance. By testing each device in the on and off state, high confidence is obtained.
Relays
Up to 24V with up to 100mA can be used to actuate relay coils. This allows testing of contacts in each state to ensure that the contacts are not shorted, and that the coil is operational.
Diodes
Diodes are tested by providing a constant current source (0.1µA to 100mA), then measuring the forward voltage drop, which is typically in the 0.6V to 0.8V range. This test ensures that the diode is installed, is in the proper orientation, and is not open or shorted.
Zener Diodes
Zeners are tested by providing a constant current source (0.1µA to 100mA), then measuring the forward voltage drop. Measurements up to 50V can be performed. This test ensures that the zener diode is installed, is in the proper orientation, and is not open or shorted. Zeners that cannot be brought to their full voltage due to current or voltage limiting can be tested as normal diodes or in some cases can be tested during the power-up stage.
LEDs
LEDs are tested like signal diodes, but normally have higher forward voltage drop. Special light-sensing probes can be added to customized test fixtures to detect brightness and color of LEDs and incandescent lamps.
Transformers
Transformers are typically tested for dc resistance of each coil to detect presence. Coils can also be tested for inductance, and a polarity test can be used to ensure that each coil is wired correctly. This can detect faults inherent to hand-loading of transformers with wire leads.
IC Presence/Orientation
IC's are tested by using the ICs test. This test measures each IC pin to specified pins such as VCC, VSS or VDD, checking for the presence of the IC's internal protection diodes. This test detects most faults such as shorted pins, open pins or mis-clocked or wrong ICs. In some cases, faults may not be detected if the IC pins are bussed or devices of similar pin-topology are interchanged.
IC Pin Connections
With the use of TestJet Technology, the System can detect opens to IC pins, even though the pin is bussed to other ICs. This advanced technology (licensed to CheckSum by Agilent), uses a sophisticated software/hardware algorithm to measure the minute capacitance between the PCB and the IC for each pin. If a pin is open, the capacitance significantly decreases. This technology can be used for most non-power and ground lines on the ICs and on many connectors to ensure proper connection and/or connector presense.
Capacitor Polarity based on TestJet Technology
In some cases, constant-current and voltage measurements of a polarized capacitor can be used to detect incorrect polarity since the capacitor draws additional current as the voltage increases in the incorrect polarity. As a practical matter, this technique cannot be used in many cases during in-circuit testing because of voltage or parallel impedance limitations. In this case, the SMT option can be used to detect the polarity of most axial/SMT aluminum and tantalum capacitors up to about 200µF.
Autoprogram and Test
To test UUTs without programming, CheckSum offers the `Autoprogram' algorithm. This allows you to place a known-good UUT on the test fixture for the System to self-program itself. Other boards can then be tested to find differences that may be indicative of faults. Detected properties include open/shorts, resistance, capacitance and diode junction presence. While this algorithm does not provide the detailed diagnostic messages of a fully-programmed UUT, it can help get boards up on the System quickly for use while programming, or as a complete test on prototype or short runs.
The Analyst ems system includes a power module that can be used to provide higher current outputs from the system. These higher current outputs can be used to actuate UUT relays, power-up low power UUTs, provide additional guard current, or apply stimulus for power-up testing. The module has dual voltage-programmable high current outputs that can be set from +12V to -12V (up to 24V differential). For switching these outputs to the UUT, 16 relay test point outputs are provided. Voltage and current output can be monitored. Fixed switched supplies provide +12V, +5V and -12V at the back panel. These outputs can be switched on or off via on-board relays. The outputs are fused for protection of the system and UUT. Eight additional digital pins can be used for digital input/output or to energize external relays.
Digital I/O Option
The Analyst ems can be configured with an optional 48 or 96 digital I/O pins. These pins can be relay-connected to the UUT in byte increments. Within each byte, each pin can be set to be an input (tri-state output) or an output. Since each pin has a 10KW pull-up (in conjunction with totem-pole outputs), it is compatible with most logic families. VCC for output can be selected to be +5V or +3.3V.
Boundary-Scan Option
The Analyst ems can be configured with the optional Boundary-Scan Test. This allows the System to be used with UUTs that have been designed to accommodate boundary-scan, or have on-board devices that support boundary-scan. In addition, boundary scan can be used by some programmable devices to perform in-system programming and program verification.
MultiWriter ISP Device Programming
The Analyst ems can be equipped with the MultiWriter ISP programming and verification capability to simultaneously program up to 384 ISP devices in-circuit.
Other System I/O
In addition to the power/stimulus/measurement capabilities already mentioned, the System has a number of other functions available. These include 8 bits of Digital I/O / Relay drivers (PWR-2) and 2 Switched grounds (PWR-2) |
