Dif­fe­ren­ti­al In-Line Charge Am­pli­fi­er

IFTA ChargeAm­pli­fi­er: Ideal for high tem­per­a­ture sen­sors

Piezo sen­sors with in­te­grat­ed am­pli­fi­er elec­tron­ics can­not be used in high-tem­per­a­ture ap­pli­ca­tions, as these can­not with­stand the tem­per­a­tures. Here, ex­ter­nal charge am­pli­fiers are used which con­vert the charge sig­nal out­side the high tem­per­a­ture zone into a volt­age or cur­rent sig­nal and can thus also trans­mit it over longer dis­tances.

The IFTA ChargeAm­pli­fi­er is an Ex nA (ATEX Zone 2) cer­ti­fied, dif­fer­en­tial in-line charge am­pli­fi­er that is spe­cial­ly tai­lored to the re­quire­ments of high-tem­per­a­ture sen­sors.

High­lights of the IFTA ChargeAm­pli­fi­er

  • Selectable gain: 0.5 ... 250 mV/pC
  • Out­put sig­nal: 10 Vpp
  • Fre­quen­cy range: 3 Hz ... 20 kHz
  • IEPE sup­ply: 4 ... 12 mA
  • Com­pat­i­ble with: ICP, CCLD, Isotron, Delta­tron, Piezotron, etc.

Data sheet ChargeAm­pli­fi­er

  • Very good sig­nal noise ratio of up to 116 dB
  • Ex­cel­lent EMC prop­er­ties
  • Dif­fer­en­tial input (sin­gle-ended ver­sion avail­able)
  • Com­pen­sa­tion for the py­ro­elec­tric "pop­corn ef­fect" with piezo­elec­tric sen­sors
  • Ex nA (ATEX zone 2) cer­ti­fied (in con­junc­tion with IFTA Ar­gusOMDS/Dy­naMaster)
  • Proven under harsh con­di­tions (up to IP65)

The Charge Am­pli­fi­er as Part of the Mea­sure­ment Chain

The IFTA ChargeAm­pli­fi­er of­fers Ex nA (ATEX Zone 2) cer­ti­fi­ca­tion for ex­plo­sion pro­tec­tion, is sup­plied via IEPE and is per­fect­ly suit­ed for piezo sen­sors in high-tem­per­a­ture en­vi­ron­ments.

Ad­van­tages of the IFTA ChargeAm­pli­fi­er

IEPE sup­ply

The IFTA ChargeAm­pli­fi­er can be in­te­grat­ed be­tween sen­sors and mea­sure­ment de­vices with­out the need for an ex­ter­nal power sup­ply be­cause it re­ceives its power from an IEPE. This sim­pli­fies the mea­sure­ment chain and makes the charge am­pli­fi­er uni­ver­sal­ly com­pat­i­ble and in­her­ent­ly short-cir­cuit-proof.

Dif­fer­en­tial input

The IFTA ChargeAm­pli­fi­er is a dif­fer­en­tial charge am­pli­fi­er that en­sures op­ti­mal pro­tec­tion against com­mon-mode noise such as mains hum, thus op­ti­miz­ing sig­nal qual­i­ty. A ver­sion with op­ti­mized CMRR is avail­able for sin­gle-ended sen­sors.

Ex­cel­lent EMC prop­er­ties

In in­dus­tri­al en­vi­ron­ments, it is im­por­tant to pay at­ten­tion to the elec­tro­mag­net­ic com­pat­i­bil­i­ty of mea­sure­ment equip­ment. This as­pect was par­tic­u­lar­ly con­sid­ered dur­ing the de­vel­op­ment of the IFTA ChargeAm­pli­fi­er and was the sub­ject of nu­mer­ous tests in the EMC lab­o­ra­to­ry and in the field.

Ex nA Cer­ti­fi­ca­tion

A ver­sion with Ex nA (ATEX Zone 2) cer­ti­fi­ca­tion is avail­able for use in haz­ardous en­vi­ron­ments. With this op­tion, the IFTA ChargeAm­pli­fi­er can be lo­cat­ed in the ATEX Zone 2 and the mea­sure­ment sys­tem can be lo­cat­ed out­side of that zone.

Cus­tomiz­able Gain

Depend­ing on the sen­sor, the ap­pro­pri­ate op­ti­mal am­pli­fi­ca­tion can be se­lect­ed. In ad­di­tion to the stan­dard am­pli­fi­ca­tions, in­di­vid­u­al adap­ta­tions can also be re­al­ized cost-ef­fec­tive­ly thanks to the mod­u­lar am­pli­fi­er con­cept.

Low Noise

In high-end A/D con­vert­ers, such as those used in the IFTA AD4 line, for ex­am­ple, 24-bit pre­ci­sion is now avail­able. To make the most of this pre­ci­sion, IFTA ChargeAm­pli­fi­er of­fers par­tic­u­lar­ly low-noise am­pli­fi­ca­tion. At 1 kHz, the SNR is 116 dB.

IFTA ChargeAm­pli­fi­er

  • Overview
  • Tech­ni­cal Data
  • Op­tions
IFTA ChargeAmplifier charge amplifier

The IFTA ChargeAm­pli­fi­er is used to con­vert dy­nam­ic charge sig­nals into a volt­age sig­nal, which can be trans­mit­ted over longer dis­tances to the mea­sure­ment sys­tem.


  • Sup­port of sen­sors that de­liv­er a charge, e.g. high tem­per­a­ture piezo sen­sors for pres­sure, ac­cel­er­a­tion or power
  • Op­tion­al­ly avail­able with cer­ti­fi­ca­tion and hous­ing for EX na (ATEX Zone 2) ap­pli­ca­tions
IFTA ChargeAmplifier charge amplifier


Num­ber of chan­nels :1
Fre­quen­cy range:3 ... 20000 Hz
Weight:175 g with­out ATEX hous­ing

Charge input

Input im­ped­ance:1 MΩ
Am­pli­fi­ca­tion:5, 10, 25, 50, 100 or 250 mV/pC
Sig­nal-to-noise ratio:up to 116 dB


Oper­at­ing point:12 VDC
Out­put sig­nal:±5 VAC
IEPE sup­ply:8 … 12 mA
IFTA ChargeAmplifier charge amplifier
  • Other am­pli­fi­ca­tions and fre­quen­cy ranges are avail­able upon re­quest
  • The fol­low­ing mount­ing op­tions are avail­able:
    • Wall mount­ing
    • DIN rail
    • Ex nA (ATEX Zone 2) cer­ti­fied hous­ing
IFTA ChargeAmplifier charge amplifier
IFTA ChargeAmplifier charge amplifier


  • Im Siemens Clean En­er­gy Cen­ter, Ber­lin führt die AD4Pro zu maßge­blich­er Kom­plex­ität­sre­duzierung bei der Mess­kette und vere­in­facht so den schnellen und fehler­freien Kon­fig­u­ra­tionswech­sel


  • Ser­vi­cein­ge­nieure wer­den mit täglich wech­sel­nden Mes­sauf­gaben kon­fron­tiert. Mit der AD4Pro sind sie auf alle Sen­sortypen vor­bere­it­et ohne zusät­zliche ex­terne Ver­stärk­er mitzunehmen


  • Bei Ladungsver­stärk­ern sind in­te­gri­erte Oper­a­tionsver­stärk­er mit di­rekt an­schließen­der A/D Wand­lung In Sachen Sig­nalqual­ität un­schlag­bar. Der Lehrstuhl für Tur­bo­maschi­nen und Flu­gantriebe der TU München setzt daher für seine Hochtem­per­atur-Piezo-Druck­aufnehmer auf die AD4Pro.

Pop­corn-Ef­fect Com­pen­sa­tion

Sen­sor crack­ers ("pop­corn ef­fect") pose a par­tic­u­lar chal­lenge for the charge am­pli­fi­ca­tion of high-tem­per­a­ture sen­sors. They occur when such a sen­sor is heat­ed so quick­ly that ther­mal stress builds up in the piezo el­e­ment. If the ma­te­ri­al sud­den­ly re­lax­es, large amounts of charge are sud­den­ly re­leased. In sim­ple charge am­pli­fiers, the so-called py­ro­elec­tric ef­fect can also over­drive the elec­tron­ics for sec­onds and thus ef­fec­tive­ly blind it.

To meet this chal­lenge, spe­cial mea­sures have been taken to min­i­mize the im­pact of this ef­fect with the IFTA ChargeAm­pli­fi­er. In ad­di­tion, the soft­ware rec­og­nizes typ­i­cal error pat­terns and can take this in­for­ma­tion into ac­count dur­ing anal­y­sis, thus avoid­ing in­cor­rect con­trol ac­tions.

The re­sult is a charge am­pli­fi­ca­tion with max­i­mum avail­abil­i­ty and re­li­a­bil­i­ty.

Ap­pli­ca­tion in Gas Tur­bines

A typ­i­cal ap­pli­ca­tion of such a mea­sure­ment chain is the mea­sure­ment of pres­sure in com­bus­tion cham­bers of sta­tion­ary gas tur­bines in order to iden­ti­fy ther­moa­cous­tic com­bus­tion in­sta­bil­i­ties. For this pur­pose, the volt­age sig­nal that the charge am­pli­fi­er gen­er­ates is sam­pled by an ana­log input mod­ule (e.g. AD4 IEPE). The IFTA Ar­gusOMDS sys­tem per­forms spe­cial analy­ses of the fre­quen­cy and time do­mains and, via a com­mu­ni­ca­tion in­ter­face with the gas tur­bine con­troller, pro­tects the ma­chine against dam­age caused by com­bus­tion os­cil­la­tions. Ef­fec­tive com­pen­sa­tion for sen­sor "shots" is par­tic­u­lar­ly im­por­tant with such ap­pli­ca­tions, so that cost­ly un­nec­es­sary ma­chine shut­downs can be avoid­ed. In com­bi­na­tion with the IFTA Ar­gusOMDS, the charge am­pli­fi­er with piezo­elec­tric high-tem­per­a­ture sen­sors is used on sta­tion­ary gas tur­bines to pro­tect against ther­moa­cous­tic vi­bra­tions in com­bus­tion cham­bers.

The Al­ter­na­tive: IFTA AD4Pro with In­te­grat­ed Charge Am­pli­fi­er

When the dis­tance to the mea­sure­ment sys­tem to be bridged is just a few me­ters, the input mod­ule IFTA AD4Pro can be used. Each input of the mod­ule has its own in­te­grat­ed com­plete charge am­pli­fi­er that can op­tion­al­ly be switched on.

Due to the charge sig­nals short trans­mis­sion paths, this de­sign en­ables op­ti­mal sig­nal qual­i­ty and flex­i­bil­i­ty. IFTA AD4Pro is also suit­able for mo­bile ap­pli­ca­tions, as ad­di­tion­al elec­tron­ics are elim­i­nat­ed. The am­pli­fi­ca­tion is con­fig­ured via soft­ware and stored along with all of the mea­sur­ing sys­tem's other con­fig­u­ra­tion data. Espe­cial­ly with larg­er test set­ups, this has the de­ci­sive ad­van­tage that changes logged for past con­fig­u­ra­tions can be eas­i­ly re­stored. Thus, sources of error will be avoid­ed and set-up is more flex­i­ble.

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