IfTA CSG: The Charge and Sig­nal Gen­er­a­tor

Test & Cal­i­brate Mea­sure­ment Chains

The IfTA ChargeSig­nalGen­er­a­tor (CSG) is a charge and sig­nal gen­er­a­tor for test­ing piezo­elec­tric mea­sure­ment chains. The light and handy de­vice can sim­u­late sen­sors, e.g. high tem­per­a­ture sen­sors for pres­sure and ac­cel­er­a­tion.

The in­tu­itive op­er­a­tion is car­ried out via func­tion keys and a 2.7 inch dis­play. Thanks to the bat­tery sup­ply, dis­play back light­ing and car­ry­ing strap, the charge gen­er­a­tor can also be used in places that are dark and dif­fi­cult to ac­cess. For dif­fer­en­tial charge sig­nals a Lemo con­nec­tion is avail­able that is iden­ti­cal to the com­mon sen­sors. Other vari­ants are cov­ered by op­tion­al adapters.

Fre­quen­cy and am­pli­tude of the out­put sig­nal are freely de­ter­mined by the user. In ad­di­tion to the si­nu­soidal wave­form, the sim­u­la­tor also of­fers an asym­met­ric wave­form to check the po­lar­i­ty of the ca­bling of a mea­sure­ment chain. The syn­chro­nous volt­age out­put can also be used to de­ter­mine trans­fer func­tions, e.g. of charge am­pli­fiers.

Through pre­cise dig­i­tal syn­the­sis, the IfTA ChargeSig­nalGen­er­a­tor of­fers high ac­cu­ra­cy and can also be used for cal­i­bra­tion. Op­tion­al­ly, the charge and sig­nal gen­er­a­tor can be cal­i­brat­ed trace­able to the na­tion­al ref­er­ence stan­dard (DIN EN ISO / IEC 17025).

Ad­van­tages of the Charge and Sig­nal Gen­er­a­tor

Test Mea­sure­ment Chains Ef­fi­cient­ly

Com­pact and light­weight de­sign, net­work-in­de­pen­dent bat­tery power and user-friend­ly op­er­a­tion save im­por­tant time dur­ing com­mis­sion­ing. Check your mea­sure­ment chains and mea­sur­ing in­stru­ments your­self and make sure that they func­tion cor­rect­ly. This saves prob­lems and time, as com­po­nents do not need to be shipped for cal­i­bra­tion un­nec­es­sar­i­ly.

Mea­sure Trans­fer Char­ac­ter­is­tics

With the syn­chro­nized volt­age out­put, the trans­fer char­ac­ter­is­tics of the charge mea­sure­ment chain can be iden­ti­fied eas­i­ly.

Find and pre­vent er­rors ef­fec­tive­ly

Func­tion­ing and well cal­i­brat­ed mea­sure­ment chains are the basis for fail­ure-free op­er­a­tion of test bench­es, en­gines and in­dus­tri­al plants. The IfTA ChargeSig­nalGen­er­a­tor en­sures this from the be­gin­ning and helps to elim­i­nate caus­es quick­ly in case of er­rors.

Typ­i­cal Ap­pli­ca­tion Sce­nar­ios of the Charge Sig­nal Gen­er­a­tor

test­ing piezo-Based mea­sure­ment chains Ef­fi­cient­ly

Some mea­sure­ment ap­pli­ca­tions with piezo-based trans­duc­ers re­quire the use of ex­ter­nal charge am­pli­fiers, usu­al­ly due to ad­verse en­vi­ron­men­tal con­di­tions. Such mea­sure­ment chains are com­plex and hence prone to er­rors.  The there­fore re­quired sup­port for the setup and trou­bleshoot­ing is pro­vid­ed by a por­ta­ble sen­sor sim­u­la­tor.

The fig­ure on the right shows a mea­sure­ment chain with ex­ter­nal charge am­pli­fi­er. A mea­sure­ment vari­able (M) gen­er­ates a charge sig­nal (Q) in the piezo-based trans­duc­er, which is trans­formed into a low im­ped­ance volt­age sig­nal (U) by the charge am­pli­fi­er. Sub­se­quent­ly, this volt­age sig­nal is con­vert­ed into a dig­i­tal sig­nal by an ana­log-to-dig­i­tal con­vert­er (A/D). The sen­sor sim­u­la­tor - in the fol­low­ing de­not­ed as charge sig­nal gen­er­a­tor (CSG) - is con­nect­ed to the mea­sure­ment chain in­stead of the sen­sor. This re­sults in four im­por­tant ap­pli­ca­tion sce­nar­ios.

 

Sce­nario 1: Cal­i­bra­tion

The over­all goal is to check the cal­i­bra­tion of the en­tire mea­sure­ment chain (with­out the sen­sor). In gen­er­al, the process of cal­i­bra­tion aims to achieve the best pos­si­ble ac­cor­dance be­tween mea­sure­ment vari­able and mea­sured value. There­fore, the charge sig­nal gen­er­a­tor is used to feed a sig­nal of de­fined am­pli­tude and fre­quen­cy into the mea­sure­ment chain. The am­pli­tude is se­lect­ed in a way that it cor­re­sponds to a typ­i­cal value of the mea­sure­ment vari­able, e.g. 1.0 g for an ac­celerom­e­ter. At the other end of the mea­sure­ment chain - rep­re­sent­ed here by a lap­top - like­wise an am­pli­tude of 1.0 g as well as the fre­quen­cy set at the charge sig­nal gen­er­a­tor should be dis­played. If this is en­sured for a num­ber of typ­i­cal input sig­nals, the mea­sure­ment re­sult ob­tained in real op­er­a­tion can later be as­sumed to be plau­si­ble. For this ap­pli­ca­tion it is im­por­tant to use a cal­i­brat­ed charge sig­nal gen­er­a­tor.

Sce­nario 2: Sig­nal path trac­ing and trou­bleshoot­ing

The goal here is to check the in­di­vid­u­al sig­nal paths. This is done ei­ther to de­tect an ex­ist­ing error or to check the mea­sure­ment chain be­fore the first com­mis­sion­ing or after a mod­i­fi­ca­tion. For this pur­pose, the CSG is con­nect­ed at dif­fer­ent points with­in the mea­sure­ment chain. For the parts of the mea­sure­ment chain - from the sen­sor point of view - after the charge am­pli­fi­er, a volt­age out­put in­stead of a charge out­put must be used. Ap­pro­pri­ate de­vices there­fore pro­vide both out­put sig­nals. For each in­stal­la­tion point, it is eval­u­at­ed how the sig­nal at the mea­sure­ment de­vice changes: Does it be­come weak­er? Do dis­tur­bances occur?  Since the anal­y­sis is com­par­a­tive, the CSG does not nec­es­sar­i­ly have to be cal­i­brat­ed. If you start the anal­y­sis at the sen­sor and then move to­wards the mea­sure­ment de­vice, this is called a for­ward anal­y­sis. If you pro­ceed the other way round, this is called back­ward anal­y­sis. In this way, in­cor­rect or bad wiring or faulty com­po­nents can be sys­tem­at­i­cal­ly found and their in­flu­ence on the mea­sure­ment re­sult eval­u­at­ed.

Sce­nario 3: Check­ing Po­lar­i­ty

For cer­tain ap­pli­ca­tions the po­lar­i­ty of the sen­sor sig­nal is of great im­por­tance, e.g. for modal analy­ses. The cor­rect po­lar­i­ty can be de­ter­mined ef­fi­cient­ly by in­sert­ing an asym­met­ric sig­nal, for ex­am­ple a sig­nal that con­tains only the pos­i­tive peaks of a sine wave. If, as shown in the fig­ure, the pos­i­tive "bumps" of the sig­nal are dis­played the wrong way round in the mea­sure­ment sys­tem, there must be an in­cor­rect wiring at some point in the mea­sure­ment chain. This lo­ca­tion can sub­se­quent­ly be nar­rowed down as de­scribed in sce­nario 2.

Sce­nario 4: Deter­min­ing the TRANSFER FUNCTION

In gen­er­al, the trans­mis­sion char­ac­ter­is­tics of a mea­sure­ment chain are fre­quen­cy-de­pen­dent. This means that a har­mon­ic input sig­nal is - de­pend­ing on its fre­quen­cy - am­pli­fied/damped or phase-shift­ed to dif­fer­ent de­grees along the mea­sure­ment chain. The de­tailed be­hav­ior is quan­ti­fied by the trans­fer func­tion of the chain, rep­re­sent­ing the am­pli­fi­ca­tion/damp­ing (gain) and the phase shift (phase) of the out­put sig­nal rel­a­tive to the input as a func­tion of fre­quen­cy. In order to eval­u­ate this func­tion for spe­cif­ic fre­quen­cies, a har­mon­ic charge sig­nal (Q) with de­fined fre­quen­cy is fed into the mea­sure­ment chain. Par­al­lel to this, a volt­age sig­nal of the same fre­quen­cy and syn­chro­nous to the Q sig­nal is fed past the mea­sure­ment chain, di­rect­ly into the mea­sure­ment de­vice. This volt­age sig­nal rep­re­sents the ref­er­ence un­af­fect­ed by the mea­sure­ment chain. From both sig­nals the value of the trans­fer func­tion for the present fre­quen­cy can then be cal­cu­lat­ed. If this is re­peat­ed for sev­er­al fre­quen­cies, it is pos­si­ble to get an im­pres­sion of the fre­quen­cy-de­pen­dent re­sponse char­ac­ter­is­tics of the mea­sure­ment chain.

Charge Sig­nal Gen­er­a­tor for Qual­i­ty Man­age­ment

op­tion: Trace­able cal­i­bra­tion ac­cord­ing DIN ISO 17025

With the mar­ket in­­­tro­­­duc­­­tion of a trace­­able cal­ib­ra­­­tion of the IfTA charge sig­n­al gen­er­­at­or to a na­­­tion­al stand­ard ac­­­cord­ing to DIN ISO 17025, it can now also be used for qual­i­ty man­age­­­ment pro­­cess­es. The IfTA ChargeSig­n­alGen­er­­at­or thus en­­­ables high­est pre­­­ci­­­sion for mo­­bile test­ing and cal­ib­ra­­­tion of meas­ure­­­ment chains in a handy for­mat.

IfTA ChargeSig­nalGen­er­a­tor CSG and CSG10

  • Overview
  • Tech­ni­cal Data
  • De­liv­ery scope and equip­ment
IfTA ChargeGenerator - charge signal generator

TWO VARIANTS - de­pend­ing on the re­quest­ed max­i­mum am­pli­tude

IfTA of­fers two ver­sions of the IfTA charge and sig­nal gen­er­a­tor that dif­fer in the max­i­mum am­pli­tude and the am­pli­tude step size:

  • IfTA ChargeSig­nalGen­er­a­tor CSG for am­pli­tudes up to 1.000 pC in 0.1 pC steps
  • IfTA ChargeSig­nalGen­er­a­tor CSG10 for am­pli­tudes up to 10.000 pC in 1.0 pC steps
IfTA ChargeGenerator - charge signal generator

Gen­er­al

Power sup­ply:4 x AA bat­tery
Di­men­sions:33 x 150 x 107 (H x W x L in mm)
Weight:271 g (with­out bat­ter­ies)

out­put

Dif­fer­en­tial charge:LEMO OS.302
Charge sin­gle-ended:BNC (fe­male)
Volt­age:BNC (fe­male)

Sig­nal ouput for charge sig­nal gen­er­a­tor CSG

Fre­quen­cy:1 ... 20000 Hz in 0.1 Hz Schrit­ten
Charge:0 ... 1000 pC in 0.1 pC Schrit­ten
Volt­age:0 ... 1000 min 0.1 mV Schrit­ten
Wave form:Sine and half sine wave

Sig­nal ouput for charge sig­nal gen­er­a­tor CSG10

Fre­quen­cy:1 ... 20000 Hz in 0.1 Hz step size
Charge:0 ... 10000 pC in 1.0 pC step size
Volt­age:0 ... 1000 min 0.1 mV step size
Wave form:Sine and half sine wave
IfTA ChargeGenerator - charge signal generator

The charge and sig­nal gen­er­a­tor is sup­plied in a prac­ti­cal car­ry­ing case in­clud­ing a mi­crodot adapter (BNC - 10-32 UNF).

The fol­low­ing adapters and adapter ca­bles are op­tion­al­ly avail­able:

  • Lemo 0S.302 - 7/16-27 UNS-2A
  • Lemo 0S.302 - wire end fer­rules
  • BNC - M4 x 0.35

The sig­nal and charge gen­er­a­tor is de­liv­ered with a fac­to­ry cal­i­bra­tion as stan­dard.

The trace­abil­i­ty of the fac­to­ry cal­i­bra­tion to a na­tion­al stan­dard (DIN EN ISO/IEC 17025) is op­tion­al­ly avail­able.

IfTA ChargeGenerator - charge signal generator
IfTA ChargeGenerator - charge signal generator