RD Controls Special Project Note:10.1
Waveform Capture System (WCS)
March 9, 1993
Table of Contents
System Description 3
Analog Front-end 4
External Connections 7
Coil Configuration 8
Gain Setting 16
Signal Integrator & Memory 17
Communication to host computer 17
Appendix A: Signal Integrator Module 18
Appendix B: Application Software 19
Appendix C: Communication Software 20
Appendix D: Schematic, PAL equations 21
This document will instruct the user on how to operate the Intermediate Prototype of the Waveform Capture System (WCS).
A system structure for the Intermediate Prototype is provided in Figure 1 and system Schematic; PAL equations can be found in Appendix D.
The system is made up of a number of components, starting with a probe which measures the field of the magnet to be analyzed. The probe is rotated by a stepping motor. The stepping motor is controlled by a stepping motor controller which gets its commands from a host computer. An optical encoder determines probe position during rotation. The probe output signals are fed into the Analog Front End which converts them into a digital signal.
The digital signal is then processed and stored by the SIM (Signal Integrator & Memory) module to be transferred, on command, to the host computer by an embedded processor. The embedded processor and SIM module are housed in a VXI enclosure. The embedded processor and the host computer are linked via a GPIB interface.
The Analog Front End provides four input channels to accommodate up to four signals from the probe. For this test run, we will use only three of them, because relays to configure the fourth channel becouse were not funded.
This document describes the workings of the WCS Intermediate Prototype box previously referred to as the Analog Front End, the SIM module, and information about the communication software.
The Analog Front-end is housed in a 16 " x 20" Hoffman enclosure supplied with ventilation holes and fan. Both ventilation holes are shielded with a screen mesh to inhibit outside noise. The part placement inside the Hoffman enclosure is shown in Figure 2. The list of parts is given in Table 1.
Table 1. List of Parts
Part # Description # of Items
1 +5V DC Digital Supply 1
2 15V DC Analog Supply 2
3 +5V DC Analog Supply 1
4 Coil Configuration Indicators 4
5 Gain Indicator 1
6 VXI V/F Board 1
7 VXI Preamplifier Board 1
8 Internal LEMO Connector for the Reversed Direction Signal 1
9 Internal LEMO Connector for the Normal Direction Signal 1
10 Internal LEMO Connector for the V/F Output Signal 1
11 Gain Rotary Switches 1
12 Coil Configuration Toggle Switches 12
13 Control Push Button Switches 2
14 Probe Input Connector 1
15 Internal LEMO connector for the V/F Board Input Signal 1
16 Internal LEMO connector for the Preamplifier Board Output Signal 1
17 External Coax Connectors for the V/F and Direction Signals 2
18 Internal LEMO connectors for the Preamplifier Board's Bucking Channels 4
Fig. 2 WCS Intermediate prototype box. Part placement.
The Digital +5V DC, 1A, power source (3 in Fig 2) supplies power to the digital part of the circuit. Two Analog 15V DC, 500 mA, power sources (2 in Fig 2) run in parallel and serve as current sources for all amplifiers in the analog part of the circuit. The Analog + 5V DC, 1A, power source (1 in Fig 2) is used to power LED indicators, relays, and their drivers. All aforementioned power supplies are made by Power Mil Inc.
The Coil Configuration Indicators (4 in Fig 2) show the user polarities of coil signals and also whether the coils are configured as source coils or as bucking coils. There is a separate indicator for each of the four channels.
The Gain Selection Indicator (5 in Fig 2) informs the user which gain setting has been selected.
The VXI V/F board (6 in Fig 2) contains the filter, a rectifier, and a V/F converter with zero crossing detector.
The VXI Preamplifier board (7 in Fig 2) contains a coil configuration circuitry and the preamplifier circuitry.
The Normal Direction Signal (9 in Fig 2) is used to increment or decrement the contents of a V/F counter inside the SIM module. The Reversed Direction Signal (8 in Fig 2) is the binary complement of the Normal Direction Signal.
The buffered V/F Output (10 in Fig 2) provides a pulse stream to be processed by the SIM module.
The Gain Rotary (11 in Fig 2) switch is used to set the Gain for the preamplifier.
Polarity, Selection and Bucking toggle switches (12 in Fig 2) are used to configure the incoming probe signal.
The two red Control Push Buttons (13 in Fig 2), set and reset the load circuit configurations defined by the Polarity, Selection, and Bucking toggle switches and the Gain rotary switches.
The probe signals are supplied via the MS3126f16-26P Burndy connector (14 in Fig 2).
Two Internal LEMO (15 and 16 in Fig. 2) Connectors provide the link between the Preamplifier board and the V/F board.
Two External Coaxial Connectors (17 in Fig 2) provide the V/F and Normal Direction signals to the SIM module.
The Internal LEMO connectors (18 in Fig. 2) link the Preamplifier board to the probe input connector (14 in Fig 2).
The Analog Front-end box is linked to the external system via connectors placed on the bottom of the box. The bottom view is shown in Figure 3 where the connectors have the following uses:
1, 2, 4, 5 - Calibration connectors
3 - Normal Direction Signal
6 - V/F Output Signal
7 - Probe Input Connector
Fig 3. Bottom view of enclosure
The Probe Input Connector's pin outs are shown in Fig 4.
Fig 4. Probe connection
The Bucking circuitry shown in Figure 5 allows the user to configure four coils. Only three coils are currently supported. Each coil can be used as a source coil or as a bucking coil. All four channels are laid out the same way. The only difference is that the relay identification numbers and the resistor numbers vary. All relay contacts are normally open when power is applied to the box, which means that all channels are selected as source channels.
Coil configurations are summarized in Table 2.
To load the coil configuration one must first set the switches on the switch panel to chose the desired configuration (see Fig 5) according to Table 2. Then in sequence, press the reset and set buttons (13 in Fig 2).
Attention: After the configuration has been loaded by pressing the reset and set push buttons all switches must be set into the off position.
When a new configuration is desired, you must first read the old configuration from the light bars (4 in Fig. 2) and reload this configuration as described above. Then and only then are you allowed to load your new configuration.
If you cannot get the system set up properly, you may start over by cycling the AC power. This will reset all relays to their normally open position and all LEDs will be on.
The coils chosen as the source coils must be connected to each other by jumpers JMP1..JMP4 (Fig 5). These jumpers can be found on the Preamplifier board. Jumper number corresponds to channel number. To connect channels to each other, pin 2 of each jumper must be jumpered to pin 3, except for the jumper of the last channel being used. Pin 2 of its jumper must be jumpered to its pin 1 to provide a return path for the input signal.
The signals from source coils are summed at the resistor R5 (Fig 5) to form an input signal. If any coil is chosen as a bucking coil, then it is connected in parallel with the resistor R5. Magnitudes of the signals from the bucking coils that are introduced into the input signal are adjusted by the bucking resistors R1..R4. Resistors R1..R5 can be found on the Preamplifier board.
Four light bars (4 in Fig 2) display the configuration of each of the four channels. Each segment, in each of the four light bars, represents the state of a particular relay. All segments, in each of the four light bars, are divided into three groups in the same manner as the relays. Definitions for each group of segments are provided in Figure 6. The left two segments indicate polarity, the next three segments are used to indicate if the coil of a particular channel has been selected as the source coil, and the next two segments indicate if the coil of a particular channel has been selected as a bucking coil. The last three bars are not used.
Fig 6. Definition of light bar segments
Fig 7 Switch panel
The preamplifier ranges from 1 to 1000, and is set by two rotary switches (11 in Fig 2). Switch positions for a particular gain are defined in Table 3.
To load a gain one must set the two rotary switches and sequentially press the reset and set push buttons.
Left Switch Right Switch Gain
1 1 1
2 1 5
5 1 10
1 10 20
2 10 50
5 10 100
1 100 200
2 100 500
5 100 1000
To select a different gain you must first reload your original setting. To accomplish this, sequentially, press the reset and set push buttons. Make sure that the Gain Selection Indicator (5 in Fig. 2) has all its segments on. Now, load a new gain. Check the Gain Selector Indicator to see if the correct segment went out. Only one segment should be out at a time. If more than one segment is out, then two or more gain resistors are selected which can cause an error in gain setting.
Definitions for the Gain Selector Indicator' segments are given in Figure 8.
Fig 8 Gain Selection Indicator
Signal Integrator & Memory
The Signal Integrator & Memory (SIM) module gets V/F and Direction signals from the Analog Front-end box via two coaxial cables. These cables are combined at one end into a 6 pin LEMO connector. At the other end, these cables are terminated by two coaxial connectors marked V/F and Direction. These connectors are attached to the Analog Front-end box. The 6 pin LEMO connector is connected to V/F input channels 1 & 2 on the SIM module. A full description of the SIM module is available in Special Project Note 6.3 Wave Capture System Signal Integrator and Memory Module in Appendix A.
Communication to host computer
A Radisys 80386 Processor is used as the WCS Intermediate Prototype embedded processor. The communication to the embedded processor is either by local keyboard, using application software given in Appendix B, or the GPIB interface with a number of commands specified in the document called "Commands", written by Miriam Bleadon. This document is provided in Appendix C.