VME502

VME502

VME502 Analog Input Card Highlights

VME502 Overview

The VME502 Analog Input Card provides data acquisition for 16 single-ended or 8 differential channels with optional expansion to 32 single-ended or 16 differential. The instrumentation amplifier is user configurable for gains 1 to 1000. Combining this with a sample-hold circuit and 12 bit A/D converter, the data acquisition section features ± 0.01% accuracy, 12 bit resolution, and conversion rates up to 25kHz.

Analog signal connections are made using reliable socket and header connectors which enables flat ribbon cable to be combined with gas tight and corrosion resistant connectors. An optional screw termination panel is also offered for simple and convenient field wire connections.

The VME502 card is a single height {3U, 100 x 160mm} VMEbus card, requires +5V power only, and has an operating temperature range of 0 to +70°C.

Optional Signal Conditioning

For low-level analog signal conditioning such as in sensor-based applications, Analog Devices 3B and 5B Series Signal Conditioning I/O subsystems offer rail-mounted industrial hardened analog signal interface modules with a single channel format and high level analog output. Optional sensor signal conditioning, transformer isolation of ±1500V, high common-mode and normal-mode noise rejection makes the 3B series and 5B series ideal for analog input signal conditioning for the VME502.

VME502 Operation

The VME502 is used to acquire analog signals and present them to the microcomputer in a digital form. The data acquisition section consists of a multiplexer, a programmable gain instrumentation amplifier, a sample-hold circuit, a 12 bit A/D converter and associated interface logic for transferring the resultant digital signal to the bus.

Multiplexer

The VME502 card has 16 analog input connections which are multiplexed, one at a time or as a pair to the input of the programmable gain amplifier. There are three multiplexer input configurations: single-ended, differential, and pseudo-differential.

Channel Expansion

The channel capacity on the VME502 can be doubled by ordering the VME502-002 version. This increases the channel capacity to 32 single-ended or 16 differential inputs. The VME501-001 version (16SE/8D) may also be field upgraded with a multiplexer expansion kit.

Programmable Gain Amplifier (PGA)

The outputs of the multiplexer are connected to a resistor programmable gain amplifier where the gain can be set to between 1V/V and 1000V/V, depending on the value of the user installed programming resistor. By using the equation, RG = 20K / (G-1), the value of the programming resistor can be determined for any gain. Thus for a gain of 10, a 2222 ohm resistor with very low temperature coefficient (±25ppm/°C) would be used. In addition to signal amplification, the PGA also provides: high input impedance (10 Mohm) and common mode signal rejection (78dB) when used in the differential configuration.

Analog/Digital Converter (A/D)

The VME502 contains a fast 12-bit, successive approximation A/D converter (AD574). Jumper selectable input ranges of 0 to +10V and ±10V used in conjunction with the programmable gain amplifier allows for a full scale input range as low as ± 10mV. The digital output of the A/D can represent the analog input voltage using either binary, offset binary, or 2's complement coding.

VMEbus Interface

The VME502 is treated as a DTB slave module that responds to the address modifier lines and maps into the VMEbus short I/O address space. The address of the board is jumper selectable so that it can be mapped in any one of 256 positions with a VMEbus short I/O base address of JJ00 where JJ is the hexadecimal equivalent of the jumper selection.

Each data function (e.g. Channel Address, A/D Data) is assigned a separate word in the address map. The address decoder recognizes the occurrence of one of the specific addresses and sends properly timed READ and WRITE signals to the selected register or buffer.

Power Supply dc/dc

The VMEbus +5V supply is all that is required to power the VME502 card. The on-board dc/dc converter is supplied with each card to convert the +5V supply to a low noise, isolated ±15V supply required by the analog circuitry.

Specifications