• Relay multiplexing
• DVM
• FET multiplexer
• Real time clock
• Bridge completion
• Digital inputs/outputs
• Counter
• Programmable D/As
• Optional RS-232C interface

The 3947A Data Acquisition/Control Unit combines the capabilities of several instruments and is a basic building block of an automatic data acquisition and control system. The 3497A will be used in an HP-IB automated system and can be viewed as a precision measurement and control computer peripheral.

The 3947A has been designed to be a very versatile and very powerful instrument. A basic 3947A consists of a mainframe that includes a front panel keyboard and display, a non-volatile real time clock, and an HP-IB interface. Available as an option is a 5 1/2 digit integrating digital voltmeter and current source that occupies a dedicated slot in the 3497A chassis. Capability is added to the 3497A by using any combination of plug-in assemblies. Available plug-in assemblies are:

• Relay Multiplexers with or without thermocouple compensation
• FET Multiplexer
• Digital Input/Interrupt
• Counters
• Strain gage/bridge completion
• Actuators
• Programmable voltage and current D/As
• Breadboard Assembly

Up to 5 assemblies can be added to a 3497A and the 3498A. Extender chassis can hold up to 10 more plug-in assemblies.

The 3497A DVM can resolve 1 microvolt signals and is ideal for the precise measurement of the outputs of thermocouples, strain gauges and other transducers. Included on the DVM is a programmable current source that allows four-terminal resistance measurements. The multiplexer assemblies switch 3 wires (Hi, Lo, and Guard) and add less than 2 microvolts of thermal offset to the measurement signal.

The 3497A card cage can hold 5 of any combination of the plug-in assemblies. This allows the multiplexing of up to 100 3-wire inputs to the DVM in a single 3497A or a single 3497A might contain 60 multiplexer channels, 16 digital inputs, 16 actuator outputs, and a DVM. By using the 3498A Extenders, up to 1000 analog channels or 1360 digital channels can be controlled, all at a single bus address.

The 3497A keyboard and display make the 3497A a very easy to use and make debugging of a 3497A based system easy. The calibration adjustments for the 3497A DVM are located behind a hinged front panel; this allows complete calibration of the DVM without removing it from the test rack. Connections to all of the 3497A assemblies are made using screw terminals, eliminating the need for soldering.

The 3497A mainframe includes a quartz-referenced, non-volatile, real-time clock. In addition to providing timing data, the clock can measure elapsed time, interrupt at a presettable time, and output a programmable pulse train.

Month:Day:Hours:Minutes:Seconds (U.S. Format)

Day:Month:Hours:Minutes:Seconds (European Format)

The 3497A DVM assembly is a systems quality, 5 1/2 digit, 1 microvolt sensitive dc voltmeter. The DVM is fully guarded and uses an integrating A/D conversion technique; this yields excellent common and normal mode noise rejection.

Included on the DVM assembly is a three level programmable current source. The current source, when used simultaneously with the DVM, can be used to make high accuracy four terminal resistance measurements with 1 milliohm resolution. Maximum speed is 300 readings per second in 3 1/2 digit mode.

Buffer Size: packed format: 100 readings; ASCII format: 60 readings

Option 010 - 20 Channel Relay Multiplexer

This assembly uses reed relays to multiplex signals to the DVM or other instruments. Each assembly switches 20 channels; each channel consists of Hi, Lo, and Guard lines. Two channels may be closed per assembly and relays may be closed in a random sequence or incremented between programmable limits. The low thermal offset of the relays make it suitable for measuring the outputs of strain gage and other transducers. Each channel can be configured with a filter of current shunt for additional flexibility.

The 020 assembly uses the same relay multiplexer as option 010 but incorporates a special isothermal connector block to allow thermocouple compensation. Two types of compensation (selectable by the user) are available. A temperature-dependent voltage is generated for software compensation; this voltage is then used in a computer program to compensate the thermocouple voltage. Hardware compensation involves inserting a voltage in the measurement circuit that automatically compensates the thermocouple voltage.

The option 030 assembly is used to multiplex input signals to a DVM in a manner similar to option 010. The option 030 assembly provides high speed, low level multiplexing. Maximum signal levels are 12 volts peak between any high, low or guard input and any other guard input, guard common or chassis ground.

Maximum sequential scanning rate: 4800 readings/s (at 60 Hz) using an 3437A Voltmeter and HP Series 200 computer (4000 readings/s at 50 Hz power).

The option 050 assembly can sense up to 16 channels of digital data. The first 8 channels can also be used as interrupt lines to detect transient signals. The assembly can accept inputs of 5, 12 or 24 volts and all functions and masks are fully programmable. A five-volt supply is provided for driving external contact closures and open collector outputs.

This option can be used to measure mechanical and low frequency electronic signals. The counter can measure the period of signals up to 100 kHz and the pulse width of signals down to 18 μs. The counter can also count up or down from a programmable start point. It can accept inputs of 5, 12, or 24 volts including CMOS, open collector TTL and passive contact closures.

The option 070/071 assemblies may be used to provide bridge completion for measuring strain gages, RTDs pressure sensors and load cells. Each card uses an internal shared half bridge and can complete 10 channels of 1/4 and 1/2 and full bridges in any combination. When used with a +5 V excitation supply (such as the 6214A) and the 3497A DVM, the assembly provides 0.1 μ sensitivity with 1 μ accuracy. Provisions are made for shunt calibration and checking gage leakage and lead resistance.

Option 110 consists of 16 mercury wetted form C (single pole-double throw) relays. Each relay can be individually closed and can switch 1A at 100V. The actuator assembly can be used to switch test fixture power or to actuate alarm bells. This flexibility of this assembly allows it to be used as a digital output or matrix switch.

Option 115 is an 8 channel high voltage actuator assembly that can switch voltages up to 252 Vrms and currents up to 2 amperes. The Option 115 assembly is ideal for switching power line voltages to small motors, alarm bells and lights, motor starters and solenoids.

Option 120 - Dual Voltage D/A
Option 130 - Dual Current D/A

Option 120 consists of two 0 to ± 10 V programmable voltage sources. These sources can be used to provide a programmable test stimulus or to control voltage programmed devices like power supplies and VCOs.

Option 130 consists of two 0 to 20 mA or 4 to 20 mA programmable current sources. These sources, especially when using the 4 to 20 mA range, can be used as transmitters in industrial current loops and can drive up to 600 ohms of total loop resistance.

Option 140 Breadboard Card

Option 140 is a breadboard card compatible with the 3497A cardcage. Using this card, 3497A users can construct special purpose assemblies that communicate with the 3497A backplane.

Option 232 to the 3497A deletes the standard HP-IB interface and adds an RS232C (CCITT/V.24) compatible interface allowing you to remotely locate the 3497A. The option 232 interface is also compatible with the new RS423 (CCITT/V.10) version of the RS449 interface.

The 3498A Extender chassis allows low cost expansion of 3497A-based systems. Each 3498A can hold up to ten 3497A plug-in assemblies. Use of one or more 3498As requires a 3497A (for control); all required connecting cables are supplied with the 3498A. Up to 13 3498As can be controlled by a single 3497A.