The Model 2790  SourceMeter Switch System is a high voltage, multichannel resistance measurement solution that speeds and simplifies electrical checks of airbag inflators and a variety of other automotive electrical test applications. It is the only commercial instrument that combines all the sourcing, measurement, and signal routing capabilities required to measure insulation resistance and conductor continuity in one compact, affordable package. Through the use of plug-in source/switch modules, the Model 2790 provides programmable high voltage and low current sourc-ing, plus multichannel switching support. This unique combination of capabilities establishes a new standard for price and performance in airbag inflator and other test applications.

Measure Extreme Resistances with Constant Current or Constant Voltage

The Model 2790 uses the forced constant-current method to measure resistances less than 1kΩ. In this technique, the instrument sources a constant current (I) to the resistance and measures the resulting voltage (V). The amount of current sourced is programmable from 0–50mA. Resistance (R) is calculated (and displayed) using the known current and measured voltage (R = V/I). A 20mV dry circuit clamp is available at sourcing levels up to 1mA for preserving the oxide layers on connectors and other  components.

For the 1MΩ to 1GΩ resistance ranges, the forced constant-voltage method is used to measure high resistance. This technique optimizes settling speed and reduces noise, allowing faster, high quality insulation resistance measurements. In addition, by applying high voltages (50–500V), the Model 2790 stresses a dielectric while simultaneously measuring its insulation resistance.

In addition to the resistance measurement functions available through the plug-in source/switch modules, the Model 2790’s built-in DMM allows it to make a full range of high precision resistance measurements as well as AC/DC voltage and current, frequency, and temperature measurements. These DMM functions are available either through front panel jacks or through the addition of a Model 7702 40-channel scanner module. In addition to the shorts/open testing performed with the standard Model 7751, 7752, and 7753 switch/control modules, a wide range of supporting measurements can be made. These supporting measurements simplify creating integrated test solutions for hybrid applications, such as testing complex automotive seating systems, which increasingly combine airbag inflators and seatbelt pre- tensioners, seat heaters, switches, motors, etc.

Newly Enhanced Memory Pattern Test Sequencer

The memory pattern test sequencer allows the mainframe to store and execute pre-programmed test sequences for increased testing throughput. Test setups can be stored as unique memory locations and either recalled by number as needed or scanned in sequence to maximize the number of tests per unit time without command transfer delays due to communication or controller.

Match the System Configuration to the Application

The Model 2790 is available in a variety of configurations to match specific application requirements:

• The Model 2790-H is a single-module system designed for both low current and high voltage ohms (10MΩ to 1GΩ) applications. This “base” system provides all the capabilities needed for electrical testing of either single- or dual-stage inflators in single position test stands (for example, test stands that test only one single- or dual-stage airbag at a time).
• The Model 2790-A, which is similar to the Model 2790-H, enables high voltage ohms measurements down to 1MΩ.
• The Model 2790-HH is configured for applications that require parallel testing or high voltage “soaking.” Like the Model 2790-H, it is designed for both low current and high voltage ohms applications and can test either single- or dual-stage inflators. However, with two plug-in modules, it also has the capacity to test two inflators at once, maximizing test throughput.
• The Model 2790-HL is designed for applications where it is preferable to segregate high voltage sourcing/ohms measurement and low current sourcing/ohms measurement into two separate modules. This design was developed for use in combination testing applications, such as inflator electrical checks of safety steering wheel or seat assemblies that also include switch or other ancillary device tests.
• The Model 2790-L is configured for low voltage source/ohms-only measurement applications, such as continuity-only testing of side/seat airbags and seatbelt pre-tensioners or other programmable I-source resistance applications in which high voltage resistance testing is not required but precise control of source current is.
• With the addition of a Model 7702 40-channel differential multiplexer module (part of the Integra family of switch/measure solutions), the Model 2790-A, -H, or -L + Model 7702 opens the door to higher channel count applications, such as hi-pot/continuity testing of connectors, harnesses, and power distribution devices up to 500V (internally sourced) up to 40 channels.

Broad Range of Measurement Capabilities

The Model 2790’s built-in DMM can make a wide variety of general purpose measurements:

• DC voltage measurements from 0.1µV to 1000V
• AC voltage measurements from 0.1µV to 750V
• DC current measurements from 10nA to 3A
• AC current measurements from 1µA to 3A
• 2-wire resistance measurements from 100µΩ to 120MΩ
• 4-wire resistance measurements from 100µΩ to 120MΩ
• Frequency measurements from 3Hz to 500kHz
• Period measurements from 333ms to 2µs
• Temperature measurements from –200°C to 630°C (thermistors and 4-wire RTDs)

Additional features of the Model 2790 mainframe include:

• Setup storage—Up to four instrument setups can be saved and recalled.
• Offset-compensated ohms—A two-measurement process for 4-wire ohms to cancel the effects of thermoelectric EMFs. Available for the 100Ω, 1kΩ, and 10kΩ ranges.
• Math—m/X+b, mX+b, percent, and four special math functions provide convenient manipulation of raw readings.
• Relative—Null offsets establish baseline values.
• Ratio and channel average—Ratio and average calculations for two switching module channels (7702)
• Buffer—Store up to 55,000 readings in the internal buffer
• Limits—Two sets of high and low reading limits to test devices
• Digital I/O port—Five digital limit test output lines to control external circuitry. An external trigger input can also be accessed at this port
• Trigger Link—Separate connector with input and output signals.
• Monitor—The Model 2790 can monitor a selected channel. A scan can be triggered to start when the monitor detects that a reading limit has been reached (7702).
• Remote interface—Model 2790 can be controlled using the IEEE-488 interface (GPIB) or the RS-232 interface.

Example Application – Dual Stage Airbag Inflator Testing–One or Two

Example Application – 40-channel Wiring Harness Testing

Three source/switch plug-in modules provide the Model 2790 with programmable high voltage and low current sources, connection switching, and signal conditioning circuitry.

Applications:

• Automotive airbag inflator/module electrical functional tests
• Seatbelt pre-tensioner actuator/module functional electrical check
• High speed, parallel soak, dual inflator, or dual test station electrical check
• Pinched wire, high voltage, insulation resistance testing in automotive seats, avionics, etc.
• Multipin connector/harness continuity and leakage resistance measurements
• Multicontact/switch dry circuit continuity and leakage tests
• Automotive power/fuse center continuity and leakage resistance characterization
• PCB/PWB and general purpose short/open circuits testing