where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

ZETEC, Inc.
Zetec is a global leader in nondestructive testing (NDT) solutions for the critical inspection needs of industries the world counts on every day, ...

880 views
Technical Discussions
elgazery
Consultant
National Institute for Standards, Egypt, Joined May 2003, 10

elgazery

Consultant
National Institute for Standards,
Egypt,
Joined May 2003
10
01:28 May-11-2001
Difference between dB and dBM

Please
there are any one can discuss me the difference between dB and dBM units for measurement attenuation.
Thank you in advance.
looking forward to recieve your valuable discussion.
elgazery@sit.nis.sci.eg


    
 
 
jean paul van Cuyck
Director
A2MS, Applied Acoustics, Materials and Systems, France, Joined Nov 1998, 13

jean paul van Cuyck

Director
A2MS, Applied Acoustics, Materials and Systems,
France,
Joined Nov 1998
13
04:16 May-11-2001
Re: Difference between dB and dBM
: Please
: there are any one can discuss me the difference between dB and dBM units for measurement attenuation.
: Thank you in advance.
: looking forward to recieve your valuable discussion.
: elgazery@sit.nis.sci.eg
.
dB or dBW relativ to 1W
dBm for dB relativ to 1 milliwatt. 0 dBm= 1 mW = -30dBW



    
 
 
Dr. Sotirios J. Vahaviolos
R & D, -
MISTRAS Group, Inc., USA, Joined Jan 2000, 15

Dr. Sotirios J. Vahaviolos

R & D, -
MISTRAS Group, Inc.,
USA,
Joined Jan 2000
15
05:43 May-11-2001
Re: Difference between dB and dBM
: : Please
: : there are any one can discuss me the difference between dB and dBM units for measurement attenuation.
: : Thank you in advance.
: : looking forward to recieve your valuable discussion.
: : elgazery@sit.nis.sci.eg
: .
: dB or dBW relativ to 1W
: dBm for dB relativ to 1 milliwatt. 0 dBm= 1 mW = -30dBW
.
Dear Mr.Elgazery
Its interesting,but these terms are used interchangeably at times, erroneously.The term dBm is used by
communications engineers and it is absolute.Most Power meters commercially available have this scale.
It is : dBm=10log(base 10)(P1/P2) at two different Power points.Power is read always across a 50 Ohm
resistor.IEEE has made this a standard and 1mW=0dBm(-40dBm is 100nW accross 50 Ohm and +20dBm is 100mW).
As far as I know dB(not DB)refers simly to gain(and loss/attenuation as -dB).It is different this time
as the equation is not Power but a simple ratio: dB=20log(base 10)(Gain or attenuation).One can have
a reference and above that reference he is talking in positive dBs(Gain) and below in negative dBs(loss
or attenuation).Such scales can then be modified as we have done for Acoustic Emission where we talk in
dBae and our refence is the "perfect" sensor giving us ONLY 1microVolt(!) Peak output noise.Anyway a
good goal.So for 40dBae a sensor/Amplifier(40dB Gain)output across a 50 Ohm resistor is 10mV.
Sotirios



    
 
 

Product Spotlight

Cygnus 6+ PRO Multi-Mode Ultrasonic Thickness Gauge

The Cygnus 6+ PRO thickness gauge is the most advance gauge within the Cygnus range with key featu
...
res including: comprehensive data logging; A-scan and B-scan display; manual gain control; Bluetooth connectivity; and much more. With its unique dual display and three measuring modes (Multiple-Echo, Echo-Echo and Single-Echo), this surface thickness gauge offers maximum versatility for inspections.
>

TVC awarded UKAS accreditation

TVC are delighted to finally announce we have been awarded UKAS accreditation for our calibration
...
laboratory. Laboratory accreditation to ISO/IEC 17025:2005 enables us to conduct the Electrical Verification of Ultrasonic Flaw Detection Equipment to BS EN 12668-1:2010. It has taken many months of hard work and we want to thank our staff for all their efforts during this massive undertaking.
>

Ultrasonic tomograph for imaging of concrete structures А1040 MIRA

Applicable for concrete inspection allowing imaging of the internal structure of objects from conc
...
rete, reinforced concrete, different stones. The operation applies pulse-echo technique at one-side access to the object. The instrument is feasible for concrete inspection for searching conduct ducts, conduits, detection of foreign inclusions, holes, honeycombing, cracks and other concrete defects.
>

SITEX CPSERIES

Teledyne ICM’s CPSERIES has been designed with a view to revolutionizing the handling and perfor
...
mances of portable X-Ray sets. Despite having managed to halve the weight of similar portable X-Ray generators available on the market (while continuing to provide the same power output), the SITEX CPSERIES generators feature a shutter, a laser pointer, a beryllium window, an aluminum filter and two integrated diaphragms (customized sizes are available upon request). Without compromising the robustness and reliability for which ICM products are renowned, the small size and light weight of the SITEX CPSERIES will radically change the way that you perform your RT inspections. And you will see a positive impact in terms of both quality and return on investment (ROI).
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window