Things to consider while selecting a Digitizer Chinmay Anand Misra Certified LabVIEW Developer Staff Applications Engineer
Things to Consider Specifications Ecosystem
Agenda Top 10 things to consider while selecting a digitizer Bandwidth Sampling Rate Sampling Modes Specification Resolution and Dynamic Range Triggering Onboard Memory Channel Density Synchronization Ecosystem Mixed Signal capability Software Analysis Capability
Bandwidth Frequency range of an input signal that can pass through the analog front end Frequency at which a sinusoidal input signal is attenuated to 70.7 percent of its amplitude
Bandwidth Use a digitizer with bandwidth at least two times the highest frequency component in the signal
Bandwidth Bandwidth can be approximated by rise time of the signal Rise Time -time taken to transition from 10 to 90 percent of signal amplitude
Bandwidth 5105 5114 5922 5122 5124 5152 5153 5154 Form Factor PCI/PXI PCI/PXI PCI/PXI PCI/PXI/ PXIe PCI/PXI PCI/PXI PCI/PXI PCI/PXI Resolution (bits) 12 8 16-24 14 12 8 8 8 SampleRate (MS/s) Bandwidth (MHz) Input Impedance Max Range (Vpp) 60 250 0.5-15 100 200 2000 2000 2000 60 125 6 100 150 300 500 1000 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω 50Ω 6/30 10/40 10 10/20 10/20 10 5 5 # Channels 8 2 2 2 2 2 2 2 Cost $4800- $9600 $3000- $6500 $7900- $12100 $6500- $14000 $7500- $13500 $5500- $10000 $7000- $12000 $9000- $14000
Sampling Rate The rate at which the analog-to-digital converter (ADC) digitizes the incoming signal
Sampling Rate NyquistTheorem -Sample rate needs to be at least twice as fast as the highest frequency component in the signal Sampling at just twice the highest frequency component is not enough to accurately reproduce time-domain signals
Sampling Rate Digitizer s sample rate should be at least three to four times the digitizer s bandwidth
Sampling Rate 5105 5114 5922 5122 5124 5152 5153 5154 Form Factor PCI/PXI PCI/PXI PCI/PXI PCI/PXI/ PXIe PCI/PXI PCI/PXI PCI/PXI PCI/PXI Resolution (bits) 12 8 16-24 14 12 8 8 8 SampleRate (MS/s) Bandwidth (MHz) Input Impedance Max Range (Vpp) 60 250 0.5-15 100 200 2000 2000 2000 60 125 6 100 150 300 500 1000 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω 50Ω 6/30 10/40 10 10/20 10/20 10 5 5 # Channels 8 2 2 2 2 2 2 2 Cost $4800- $9600 $3000- $6500 $7900- $12100 $6500- $14000 $7500- $13500 $5500- $10000 $7000- $12000 $9000- $14000
Sampling Modes Real-time sample rate describes the clock rate of the ADC and indicates the maximum rate an incoming signal can be acquired in a singleshot acquisition Equivalent-time sampling is a method of reconstructing a signal based on a series of triggered waveforms that are each acquired in single-shot mode
RIS Bin 1 Bin 2 Bin 3
Sampling Modes Digitize r Model Chann els Real-Time Sample Rate Equivalent- Time Sample Rate Bandwidth Resolutio n NI 5152 2 2 GS/s 20 GS/s 300 MHz 8 Bits NI 5114 2 250 MS/s 5 GS/s 125 MHz 8 Bits NI 5124 2 200 MS/s 4 GS/s 150 MHz 12 Bits NI 5122 2 100 MS/s 2 GS/s 100 MHz 14 Bits NI 5105 8 60 MS/s 60 MHz 12 Bits NI 5922 2 500 ks/s to 15 MS/s 6 MHz 16 to 24 Bits User- Defined
Resolution and Dynamic Range Number of bits returned by the ADC is the digitizer s resolution
Resolution and Dynamic Range Dynamic range is a ratio of the maximum signal and minimum signal that can measured at a single time Expressed in decibels Dynamic Range (db) = 20 x log (Maximum Voltage / Minimum Voltage) The ability of the digitizer to measure small signals in the presence of large ones
Resolution and Dynamic Range One of the reasons for using a high-resolution digitizer is to measure small signals Why not just use a lower resolution instrument and a smaller range to zoom in on the signal to measure small voltages?
Resolution and Dynamic Range 5105 5114 5922 5122 5124 5152 5153 5154 Form Factor PCI/PXI PCI/PXI PCI/PXI Resolution (bits) SampleRate (MS/s) Bandwidth (MHz) Input Impedance Max Range (Vpp) PCI/PXI/ PXIe PCI/PXI PCI/PXI PCI/PXI PCI/PXI 12 8 16-24 14 12 8 8 8 60 250 0.5-15 100 200 2000 2000 2000 60 125 6 100 150 300 500 1000 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω/1MΩ 50Ω 50Ω 6/30 10/40 10 10/20 10/20 10 5 5 # Channels 8 2 2 2 2 2 2 2 Cost $4800- $9600 $3000- $6500 $7900- $12100 $6500- $14000 $7500- $13500 $5500- $10000 $7000- $12000 $9000- $14000
Triggering Trigger is an event Digitizer s triggering capability allows you to isolate this event and capture the signal before and after the event Most digitizers and oscilloscopes include analog edge, digital, and software triggering Window, hysteresis, and video triggering featured on theni 5122,NI 5124andNI 5114
Triggering Reference (Stop) Trigger Types NI 5112 NI 5114 NI 5122 NI 5124 NI 5922 Immediate, Analog Edge, Digital Edge, Hysteresis, Window, Software Immediate, Analog Edge, Digital Edge, Hysteresis, Window, Software, Video Immediate, Analog Edge, Digital Edge, Hysteresis, Window, Software, Video Immediate, Analog Edge, Digital Edge, Hysteresis, Window, Software, Video Immediate, Analog Edge, Digital Edge, Hysteresis, Window, Software Reference (Stop) Trigger Sources CH 0, CH 1, TRIG, PFI<1..2>, RTSI<0..6>, PXI STAR CH 0, CH 1, TRIG, PFI<0..1>, RTSI<0..7>, PXI STAR CH 0, CH 1, TRIG, PFI<0..1>, RTSI<0..7>, PXI STAR CH 0, CH 1, TRIG, PFI<0..1>, RTSI<0..7>, PXI STAR CH 0, CH 1, TRIG, PFI<0..1>, RTSI<0..7>, PXI STAR Trigger Coupling AC, DC AC, DC, LF Reject, HF AC, DC, LF Reject, HF AC, DC, LF Reject, HF DC (External TRIG Reject, AC + HF Reject, AC + HF Reject, AC + HF Input) Reject Reject Reject Trigger Coupling (Analog Input Channel) Trigger Holdoff AC, DC From trigger to first point of next record Same as input channel, HF Reject, LF Reject From trigger to trigger Same as input channel, HF Reject, LF Reject From trigger to trigger Same as input channel, HF Reject, LF Reject From trigger to trigger Same as input channel From trigger to trigger Trigger Delay Y Y Y Y Y External TRIG Input Impedance 1 MΩ, 50 Ω 1 MΩ 1 MΩ 1 MΩ 1 MΩ
Onboard Memory Digitizers can sample data at several GS/s Data is transferred from the digitizer to the PC for measurements and analysis Data transfer rate to the PC is limited by bandwidth of the connecting bus such as PCI, USB, GPIB
Onboard Memory Onboard memory enables digitizers to acquire the signals at the maximum rate, store it, and later fetch the data to the PC for processing More onboard memory lets you sample at a high sample rate for a longer period of time to capture more points
Onboard Memory Onboard memory not only increases acquisition time, but also provides frequencydomain benefits
Onboard Memory Digitizer Model Channels Real-Time Sample Rate Equivalent-Time Sample Rate Bandwidth Memory Options NI 5152 2 2 GS/s 20 GS/s 300 MHz 16 MB, 128 MB, 512 MB, 1 GB NI 5114 2 250 MS/s 5 GS/s 125 MHz 16 MB, 128 MB, 512 MB NI 5124 2 200 MS/s 4 GS/s 150 MHz 16 MB, 64 MB, 512 MB, 1 GB NI 5122 2 100 MS/s 2 GS/s 100 MHz 16 MB, 64 MB, 512 MB, 1 GB NI 5105 8 60 MS/s 60 MHz 16 MB, 128 MB, 512 MB NI 5922 2 500 ks/s to 15 MS/s 6 MHz 16 MB, 64 MB, 512 MB, 1 GB
Things to Consider Specifications Ecosystem
Channel Density Important factor in a digitizer purchasing decision is the number of channels on the instrument or the ability to add channels by synchronizing multiple instruments
Synchronization Automated test applications frequently involve multiple types of instruments such as digitizers, signal generators, digital waveform analyzers, digital waveform generators, and switches Most of the times these instruments need to be synchronized
Synchronization Inherent timing and synchronization capability of PXI and NI modular instruments allows you to synchronize all these types of instruments without the need for external cabling Synchronization and Memory Core (SMC) -the common architecture for all NI high-speed modular instruments
Mixed Signal Capability SMC enables PXI Platform and NI Modular Instruments to come together as a system capable of handling mixed signals PXI digitizer can be used with arbitrary waveform generators and digital waveform generator/analyzers to build a complete mixed-signal application with the benefits of both an oscilloscope and a logic analyzer
Software, Analysis Capability, and Customizability Boxed oscilloscope provides many of the standard functions Not enough to solve every application Modular digitizer leverages the PC architecture while letting you customize an application to your requirements
Software, Analysis Capability, and Customizability NI digitizers are all programmed using the free NI- SCOPE driver software More than 50 prewritten examples NI-SCOPE Soft Front Panel provides a familiar interface similar to an oscilloscope Same hardware can be programmed for both common and custom measurements Same driver can be used with LabWindows/CVI, Visual Basic, and.net
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