RB8905 -- High Speed 12-bit ADC with 32kByte Buffer
Purpose
Measure a voltage trace.
Description
Module RB8905 is a 1 Mega-sample per second 12-bit analog to digital converter with a 32 kByte on-board data buffer.
The module has a single analog input and a clock input to do a series of data acquisitions. The number of samples to store on-board is programmable.
Module RB8905 contains the following parts:
- a track and hold
- a 12-bit ADC
- an address counter
- a 32 kByte on-board data buffer
The ADC can be programmed for bipolar or unipolar use. The input voltage span of the ADC is configured at production time for 10 V or 20 V.
The analog to digital converter IC is an ADC601 manufactured by Burr-Brown. This 12-bit ADC normally converts samples at a rate of 1 Ms/s (900 ns), but it also can convert at a rate of 2 Ms/s (400 ns). In the latter case, only eight bits are determined and this mode of operation is called short-cycle mode (fast mode, 8-bit result).
The number of samples to store on-board can be specified in one of two ways (normal conversion mode assumed):
1. 1--128 samples: specified by JMP3 on the module's board
2. 256--16384 samples: specified programmatically
The number of samples to store on-board can be specified with VI RB8905 ADC12 Set Capacity. Specifiying zero for the number of samples, or capacity, selects the JMP3 setting. For 256 and more samples, the number of samples is a power of two: 256, 512, 1024 etc.
Configuration
At production time, the ADC is configured for an input voltage range of 10 V or 20 V.
The following table shows the volt-per-bit values for the various input voltage spans.
Voltage span | volt-per-bit bipolar
---------------+--------------------------
0 .. 10 V | 2.442002 mV no
-5 .. 5 V | 2.442002 mV yes
-10 .. 10 V | 4.884004 mV yes
Note that when the ADC's fast conversion mode (8-bit result) is used, the input voltage span is reduced with a factor of 16 (2^4). See RB8905 ADC12 Get Min Input Voltage and RB8905 ADC12 Get Max Input Voltage.
Default configuration
rb8905_adc12 "name"
{
address = 0xBC
volt_per_bit = 2.442002 m
}
When the Rulbus configuration file is read, an ADC is configured as follows:
- normal conversion mode
- bipolar mode
- 256 samples
-Rulbus interrupt disabled
Modules | |
| RB8905 ADC12 Arm | |
| arm ADC for data-acquisition; a sample is taken each clock-pulse. | |
| RB8905 ADC12 Close | |
| close the ADC specified by handle. | |
| RB8905 ADC12 Get Capacity | |
| get the number of samples to acquire in the on-board buffer | |
| RB8905 ADC12 Get Jmp3 Capacity | |
| get the JMP3 setting for the number of samples to acquire in the on-board buffer. | |
| RB8905 ADC12 Get Max Input Voltage | |
| the highest acceptable ADC input voltage; takes mode settings into account. | |
| RB8905 ADC12 Get Min Input Voltage | |
| the lowest acceptable ADC input voltage; takes mode settings into account. | |
| RB8905 ADC12 Get Offset Voltage | |
| the ADC bipolar input voltage offset [V]. | |
| RB8905 ADC12 Get Voltage Span | |
| the ADC input voltage span. | |
| RB8905 ADC12 Get Voltperbit | |
| the ADC's input sensitivity configuration. | |
| RB8905 ADC12 Open | |
| open a RB8905 12-bit ADC by its name. | |
| RB8905 ADC12 Read Value | |
| read nelem samples as ADC code. | |
| RB8905 ADC12 Read Voltage | |
| read nelem samples as ADC input voltage. | |
| RB8905 ADC12 Set Capacity | |
| set the number of samples to acquire in the on-board buffer. | |
| RB8905 ADC12 Set Fast Mode | |
| set converter to fast conversion mode or to normal mode. | |
| RB8905 ADC12 Set Unipolar Mode | |
| set converter to unipolar mode or to bipolar mode. | |
| RB8905 ADC12 TEST | |
| test the ADC12 VIs and physical ADC module. | |
| RB8905 ADC12 isFast Mode | |
| true if fast (short-cycle) mode is selected (8-bit data). | |
| RB8905 ADC12 isReady | |
| true if all samples have been measured or if all samples have been read-out. | |
| RB8905 ADC12 isUnipolar Mode | |
| true if unipolar mode is selected. | |