VDSP-431 System & Functional Block Diagrams
VDSP431M
This module is an intelligent DSP base VME module . It can support up to 3 VDSP_SCM
module. The primary features of the VDSP431M are as follows:
- VMEbus A16/D16, A24/D16 and A32/D32 Slave Interrupter
- VMEbus Global intercommunication register.
- Local 128K x 32-bit zero wait state SRAM
- Local 512K x 32-bit Shared RAM with VMEbus
- One 512K X 8-bit EPROM
- 20 TTL digital I/O lines
- One RS232C serial interface
- One Serial port interface able to transfer up to 4 Mbit/S.
- Internal trigger driven by 32-bit timer/counter to all channels
- External Front Panel trigger IN
- External Front Panel trigger OUT
- Software Trigger from VMEbus using Programmable Global Register
- Integrated DSP (Digital Signal Processor) running at 32 MHz
- P2 master interface with VDSP_SCM module using P2 backplane.
- Nullpace Input/output signal
- Software watchdog
- Full Instruction block firmware that facilitate communication with the Host Processor.
The VDSP-SCM module is a servant carrier that is populated with :
- Two Strain Gauge/Bridge channels
- Two LVDT channels
- Two Valve driver channels
- Four A/D converters to digitize DC and AC parameters
- Up to 20 Digital I/O channels
- Four channel D/A monitors
- Two A/D channels for monitoring valve and excitation current
- Calibration resistance for software controlled “shunt calibration”
- DC/DC converter for the analog circuitry.
A/C Signal Conditioning
The A/C module is designed around the AD698 LVDT signal conditioner from Analog Devices. The excitation frequency can be set between 20 Hz and 20 KHz by changing capacitors. The VDSP431 AC Module is preset to 10 KHz at the factory. The output of the LVDT demodulator is amplified by the same circuitry utilized by the DC Module. Programmable relays allow the LVDT demodulator to be bypassed. This is so the AC Module can be used to support DC high-level inputs such as a DCDT. The AC excitation can be disabled when DC high-level mode is used. Two fourth order filters, with a cut-off frequency of 500 HZ, remove any residual carrier signal from the demodulator output. The LVDT modules excitation is preset at the factory to 7.0 Vpp at 10.0 KHZ. The demodulator gain is set to output +/- 9 Vdc over full stroke of the LVDT.
D/C Signal Conditioning
Incoming low level LoadCell signals are amplified by high precision low noise, low offset, high impedance instrumentation amplifier. The SCM PGA Modules utilize a two stage instrumentation amplifier design that is able to provide any gain between 1 and 5000.
- First stage G = 1 , 100,125,200,333
- Second stage G = 1, 2, 4, 8,16
The PGA module containes a differential voltage power amplifier that is controlled digitally by a 16-bit D/A. The output voltage is proportional to the D/A output voltage. A +5v D/A output is translated in a 10 V peak-peak excitation voltage. The maximum output is 18v peak to peak into a 100? load. Remote sense lines can be incorporated to compensate for voltage drops due to long wire lengths.
Value Driver
The Valve driver module is able to drive up to 100 ma into a 200 ohm load. The output of a 16-bit D/A converter drives two power amplifiers that convert the input voltage signal to a current signal. Output of the current is directly proportional to the input signal. The current range is programmable by software using relays.
Four ranges are available :
- 12.5 ma
- 25.0 ma
- 50.0 ma
- 100.0 ma
Current selected is calculated with an input voltage of 5 V.Overdrive can be up to 100 %. The actual current delivered to the valve can be monitored by the DSP. A differential amplifier converts the output current to a voltage signal directly proportional to the current flow into the load.
Load Cell configuration
