Agilent Digital Measurement Forum - Keysight€¦ · Q) Which of the following statement is FALSE? 1) Probing accessories, such as grabber tips and long ground leads, can degrade

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7 MORE hints for better scope probing


Agenda

Hint #1 – What is the system bandwidth?

Hint #2 -- Voltage measurement at high or low temperature

Hint #3 – Extending the dynamic range of InfiniiMax probe

Hint #4 – Beware of deratings over frequency

Hint #5 -- Use accessories to get the most from your probe

Hint #6 – Make hands free probing

Hint #7 – Make safe floating measurements


Quiz #1

You have a 1 GHz bandwidth scope and 1 GHz bandwidth probe connected to the scope, what will be the actual bandwidth at the probe tip?

1) > 1 GHz2) 1 GHz3) < 1 GHz


Hint #1 : What is the system bandwidth?Scope and probe bandwidth is defined as the frequency in the response where the amplitude has decreased by 3dB

If you measure 100MHz, 5V sine wave with a 100MHz scope, you will get 100MHz, ~3.5V (3dB down from 5V).


Hint #1 : What is the system bandwidth?

Weakest “Link” Determines Bandwidth

Probe BWScope BW

Connection Bandwidth

System bandwidth can be viewed as a chain reaction, where the lowest performance component in the measurement system will limit the bandwidth of the measurement.

Sample Rate



System Bandwidth is the combination of scope and probe bandwidth.

1) Passive probes• With scope’s 1 Mohm input – bandwidth is limited to

~500 MHz max• With scope’s 50 ohm input – you may achieve >500

MHz bandwidth with limited input R (e.g., 500ohm for 10:1).

2) Active probes• For Gaussian response scope/probe –

• For Brick wall response scope/probe (InfiniiMax probe, for example) – refer to the manufacturer’s recommendation

Trsystem = √Trscope2 + Trprobe2 where Tr = 0.35/BW


Hint #1 : What is the system bandwidth?Caution – probe accessories affect the bandwidth, too (connection bandwidth)!



How much of probe bandwidth is needed for me? As a rule of thumb.. for Gaussian response probe,

• For visualization -- 2 to 3 times DUT BW

• For characterization and troubleshooting – 3 to 5 times DUT BW

• For validation -- 5 times DUT BW

• For compliance testing -- 5 to 7 times DUT BW

where DUT BW = 0.35/fastest rise time (10% to 90%). You may need “less” bandwidth with Brick wall response probe. Follow the manufacturer.


Hint #2 : Voltage measurement at high or low temperature

• Automotive electronics thermal testing -- -55 ºC to +150 ºC• Testing beyond normal operating temp range of ICs -- -25 ºC to 80 ºC• environmental testing of cell phone, HDD storage device, and consumer electronics

Who needs probing under extended range of temperature?



InfiniiMax probing system with probe heads and N5450A high temperature cable -- Industry’s first probing solution for making oscilloscope measurements in environmental chambers and in other settings with extreme temperature conditions

This part stays outside the chamber and is connected to scope.

With N5381A differential solder-in head, you can test -55 ºC to +150 °C for 250+ cycles.

This part goes inside the chamber.



InfiniiMax probe bandwidth is not affected with the use of high-temp extension cable (N5450A).


Hint #3 : Extending the dynamic range of InfiniiMax probe

+

-

OscilloscopeZO = 50Ω

50Ω

50Ω50Ω25KΩ

200 fF

ZO=50Ω

50W RF Connector

+sig

ZO=50Ω

200 fF-sig

50Ω25KΩ

Probe Cable~ 5 mm ~ 10 cm Probe Amplifier



N2880A InfiniiMax In-line Attenuator

• Increases input dynamic range up to 50Vpp and offset range up to +/-30V (with 20dB attenuator)

•Pairs of 6, 12, and 20 dB attenuators in a kit

N2881A InfiniiMax DC blocking cap

•Blocks out input DC component•Withstand up to 30V dc• A pair of DC blocking caps• Can be used with in-line attenuators



• Performance (BW/rise time) is not degraded when using attenuators.• Max input voltage of the probe head is unchanged at 30V from ground.• Larger attenuation ratios will degrade the noise performance and gain of the probe system.• Need to manually select the correct scale factor in the probe menu.


Quiz #2

Q) Which of the following statement is FALSE?

1) Probing accessories, such as grabber tips and long ground leads, can degrade a probe’s performance.2) Due to advances in technology, today’s modern probes perfectly reproduce your signal under test.3) Probes become part of a circuit under test, and all probes load the circuit under test to some degree.4) Any scope probe derates the amplitude characteristics over frequency.


Hint #4 : Beware of frequency deratings

Melted current probe, why?



• Customer’s current signal – 20kHz, 100A

• Agilent N2781A current probe specs

What’s wrong with the probe?



• Any scope probe or scope derates over frequency. • Because of core saturation on current probe transformer, max input range is limited.

Customer’s signal was well over the max input range due to derating characteristics of the probe



RecommendationCheck the probe manual (user’s guide) and observe any derating information. Keep in mind that max input rating may decrease with increasing frequency. Choose a probe with enough margin for your signal frequency.


Hint #6 : Use accessories to get most out of your probe

Reference signal with 237 psec edge Measured with 500MHz

passive probe with 15 cm ground lead – reading 1.23 nsec

Measured with 500MHz passive probe with short spring ground –reading 753 psec

Measured with 1.5GHz passive probe with spring ground –reading 396 psec


Hint #6 : Use accessories to get most out of your probe – For use with new N2870A Series passive probes Short circuit-proof ,

low loading probing with IC adapter, ground blade and ground copper pad

Probing SMT chip resistor couldn’t be easier with optional micro SMD clip

PCB adapter socketMicro IC clips

Dual lead adapter

Use a probe holder to get hands free probing


Hint #6 : Use accessories to get most out of your probe

Recommendation

Probing accessories, such as grabber tips and long ground leads, can degrade a probe’s performance. Use as short a probe tip connection as possible if optimum signal integrity measurement is pursued.


Hint #6 : Make hands free probing

Well.. there must be a better way to do hands-free probing…


Hint #6 : Make hands free probing

N2787A 3D probe positioner

N2786A 2-leg probe positioner•Low cost probe positioner for hands-free probing

•Supports most 2.5mm and 5mm passive probes

•Accurate and safe positioning

N2787A 3D probe positioner•Articulated probe positioner for 3D(XYZ) hands-free probing

•Stepless 3D clamp system•Sturdy base for desktop application•Adaptable to most Agilent probes including InfiniiMax browsers

Quick and easy-to-use probe positioners for hands-free probing

N2786A 2-leg positioner


Hint #6 : Make hands free probingAgilent probe positioner comparison chart

N2786A two-leg

N2787A 3D N2784A 1-arm browser

N2785A 2-arm browser

Probe compatibility*

Agilent passive probes and SE active probes

Most of Agilent’s probes including InfiniiMax browsers

Target applications

Quick XY positioning

XYZ positioning Quick and stable XY browsing

Note *: Refer to the probe positioners data sheet for more details of probe compatibility (Agilent literature number: 5989-9131EN)


Hint #7 : Make safe floating measurementTypical floating measurement methods

isolation transformer

disconnecting power line ground

battery powered oscilloscope

differential probeCh 1 – Ch 2Unsafe and Dangerous!


Hint #7 : Make safe floating measurement Differential probes offer a safe and accurate way

Differential Probe Benefits• Safe and reliable• Accurate• High CMRR


Hint #7 : Make safe floating measurementDifferential probe benefit -- High CMRR

SignalTransmission Line

MagneticCoupling

CapacitiveCoupling

V+

R2

R1+

-

VOUTPUT

PowerLine

60 Hz V-

• Common mode rejection ratio (CMRR) = differential gain / common mode gain• Higher the CMRR, the greater the ability of probe to reject common mode signal.


Hint #7 : Make safe floating measurementDifferential probe benefit -- High CMRR


Hint #7 : Make safe floating measurementNew 100MHz/25MHz high-voltage differential probe for power measurements

N2790A N2791ABandwidth 100 MHz 25 MHzAttenuation 50:1 or 500:1 10:1 or 100:1Max input range

<1.4kV diff, <1kV common mode

<700V diff, <700V common mode

Probe interface AutoProbe BNCProbe power Via scope

AutoProbeBatteries or via USB port

Compatibility InfiniiVision and Infiniium with 1 Mohm AutoProbe input

Any 1 Mohminput, replacing N2772A HVDP

N2790A 100 MHz 1.4kV

N2791A 25 MHz 700V


Quiz #3

Q) What is the benefit of using differential probe over single-ended probe in measuring floating signals?

1) Differential probe offers safer and more reliable way of measurement.2) Differential probe offers more accurate way of measurement3) Differential probe offers higher CMRR 4) All of above


Summary

Hint #1 – What is the system bandwidth?

Hint #2 -- Voltage measurement at high or low temperature

Hint #3 – Extending the dynamic range of InfiniiMax probe

Hint #4 – Beware of deratings over frequency

Hint #5 -- Use accessories to get the most from your probe

Hint #6 -- Hands free probing

Hint #7 – Make safe floating measurements


For more information about Agilent’s scopeprobes and accessories

Publication Title Publication Type Agilent’s publication Number

Agilent Oscilloscope Probes and Accessories Selection guide 5989-6162EN

Agilent Oscilloscope Probes and Accessories 2-page selection guide 5989-8433EN

N2870A Series passive probes and accessories Data sheet 5990-3930EN

Agilent probe positioner data sheet Data sheet 5989-9131EN

Infiniium Oscilloscope Probes and Accessories Data sheet 5968-7141EN

InfiniiVision 5000, 6000 and 7000 Series Oscilloscope Probes and Accessories

Data sheet 5968-8153EN

Extending the range of Agilent InfiniiMax probe Application note 5989-7587EN

Visit www.agilent.com/find/scope_probesOr check out the literature below.

http://www.agilent.com/find/scope_probes


Reliable measurements start with probing!

Documents

Agilent Digital Measurement Forum - Keysight€¦ · Q) Which of the following statement is FALSE? 1) Probing accessories, such as grabber tips and long ground leads, can degrade