Gbs-elektronik MCA166-USB Influence of P/Z setting on peak area a Manuel d'utilisateur télécharger pdf

Application Note

Influence of P/Z setting on Peak area and lower spectrum

cutoff with MCA166

6.4.2000

Jörg Brutscher

GBS Elektronik GmbH

Problem:

Correct P/Z setting is something which is often neglected when doing measurements with the MCA166. P/Z is

mainly thought to have influence on Peak shift and Peak broadening at higher count rates. But there are other

disadvantageous effects of incorrect P/Z setting. Wrong P/Z setting seems to be a fault often made, and the

connection of P/Z setting with increased thresholds and faulty peak areas is not apparent.

The problem is that the autothreshold circuit and also the PUR (Pile up rejector) use the reverse polarity of the

shaping amplifier output as a reference for noise measurement. If there is a severe underpolezero adjustment,

then the autothreshhold circuit gets the signal that there is increased noise in the system and the lower level

threshold is increased.

These weird false P/Z setting effects get especially significant:

-If the interest is in low energy peaks, but there are also high energy peaks present.

- at long shaping times

-with high count rates

-with high amplification factors.

What is P/Z (Pole Zero) adjustment?

The shaping amplifier converts the

voltage step function signals delivered by

the detector preamplifiers to gaussian

shaped pulses, which amplitude can be

easily measured by the ADC.

Unfortunately, the gaussian pulse returns

exactly to baseline only for a single

preamp signal decay time constant. As

this time constant differs with different

preamplifiers, there will be always some

overshoot or undershoot on the shaping

amplifier output signal (see Fig. 1). The

over- or undershoot can now cause a close

following pulse to be measured with an

incorrect amplitude.

To adjust this over- or undershoot to zero,

the P/Z setting is introduced.

P/Z can be set by choosing PZC

adjustment in the menu setup-amplifier.

The P/Z adjustment of the MCA 166 can

compensate preamp signal decay time

constants from 40 µs to infinite.

0 20 40 60 80

Time (µs)

Overpolezero

Underpolezero

Correct pole zero setting

MCA 166 shaping amplifier test output

with different P/Z settings.

shaping time 2µs, amplification 150,

2" Crismatec detector with Am241 source.

Fig 1: Signal measured at the MCA 166 shaping amplifier test

output. Wrong P/Z setting distort the amplitude measurement of

close following pulses

1 2

Résumé du contenu

Page 1 - Application Note

Application NoteInfluence of P/Z setting on Peak area and lower spectrumcutoff with MCA1666.4.2000Jörg BrutscherGBS Elektronik GmbHProblem:Correct P/Z

Page 2 - Lower Cutoff channel

ExperimentAn Experiment was carried out topoint out the effects of wrong P/Zsetting. The conditions were chosensuch that the effects

Commentaires sur ces manuels

Pas de commentaire

Gbs-elektronik MCA166-USB Influence of P/Z setting on peak area a Manuel d'utilisateur

Naviguer en ligne ou télécharger Manuel d'utilisateur pour Équipement Gbs-elektronik MCA166-USB Influence of P/Z setting on peak area a. GBS Elektronik MCA166-USB Influence of P/Z setting on peak area and lower spectrum cutoff User Manual Manuel d'utilisatio

Résumé du contenu

Commentaires sur ces manuels

Produits connexes et manuels pour Équipement Gbs-elektronik MCA166-USB Influence of P/Z setting on peak area a