Test Ideas: Emulate SPI signals with a digital I/O card
By Andy Street, Autoliv Electronics, Lowell, MA, 06/01/2009

When developing a design-verification tester for millimeter-wave SOC (system-on-chip) devices, my co-workers and I needed to combine switching, electrical measurements, temperature measurement, a parallel digital interface, and a serial digital interface into one instrument.

Test Ideas: Program resistance in a bridge circuit
By Alexander Bell, Infosoft International, New York, NY, 05/01/2009

Sensors such as strain gages, RTDs (resistance temperature detectors), and thermistors produce a resistance that's proportional to force or temperature. If you measure a sensor's resistance, you can calculate the physical parameter. Circuits such as resistance bridges can help you measure the unknown resistance.

Test Ideas: Serial port tests digital circuits
By Yury Magda, Consultant, Cherkassy, Ukraine, 04/01/2009

A PC's serial port provides signal lines that you can use to expand the number of input signals. With some additional circuitry tied to these lines, you can use the port to test digital TTL logic-level circuits.

Test Ideas: Bias current modulation eliminates wiring errors
By W. Stephen Woodward, Consultant, Chapel Hill, NC, 03/01/2009

Diodes make good temperature sensors, but they require an excitation current to produce a PN-junction voltage. That excitation current causes voltage drops in measurement wires because of a wire's resistance. You need to compensate for those voltage drops so that the measurement will accurately represent the diode voltage.

Test Ideas: Generate a swept sine in LabView
By Sean McPeak, University of California, San Diego, 02/01/2009

To implement a swept sine wave with a multifunction data-acquisition card, you need to generate the data points and send them to the card. You can create a swept sine function in LabView with just one virtual instrument that can control start and stop frequencies, sample rate, and sweep duration.

Test Ideas: Produce AC test signals
By Tiger Zhou and Robert Dobkin, Linear Technology, 12/01/2008

AC testing of electronic systems often requires a low-distortion signal source to excite a DUT. Instead of using a signal generator and a power amplifier to produce a low-distortion AC signal, you can build a power oscillator with just one IC and a few discrete components.

Test Ideas: Isolate your clock source
By Daniele Danieli, EUROCOM-PRO, Venice, Italy, 11/01/2008

Circuits such as PLL synthesizers, high-dynamic-range ADCs, and timing-sensitive digital networks require a stable and spurious-free clock. Testing these circuits is often difficult if you use a master oscillator, even if the oscillator's signal meets the application's requirements for phase noise and spurious response.

Test Ideas: Serial port controls ADC
By Yury Magda, Consultant, Cherkassy, Ukraine, 10/01/2008

Engineers often need simple measurement circuits that connect to a PC. When you don't have the resources to buy a digitizer for low-speed signals, you can build one yourself with just two ICs connected to a PC's serial port.

Test Ideas: DPGA conditions signals with negative time constant
By W. Stephen Woodward, Consultant, Chapel Hill, NC, 09/01/2008

Digitally programmable gain amplifiers (DPGAs) amplify or attenuate analog signals, which maximizes an ADC’s dynamic range. Instead of using a monolithic DPGA, you can use two op amps and three analog switches to build a DPGA that is based on negative time constants.

Test Ideas: Sync sine waves over three decades
By Alfredo H. Saab and Tina Alikahi, Maxim Integrated Products, 08/01/2008

Our debut Test Ideas column describes a circuit that can synchronize a sine-wave output through three decades of frequency, while maintaining low total harmonic distortion and constant amplitude.