IfTA Char­­geSi­g­nalGe­­ne­ra­t­or: 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


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


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

Sig­nal ouput for charge sig­nal gen­er­at­or CSG

Fre­quency:1 ... 20.000 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 ... 20.000 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

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.