4-channel Bipolar Picoammeter with Analog Monitors and Bias Voltage

4-channel simultaneous sampling bipolar electrometer with 3 input current ranges (24 bit), 10/100 Mbit Ethernet connectivity and Trigger Input

  • Overview
  • Features
  • Technical specifications
  • Ordering options
  • Documentation
  • Software/Firmware


The AH501D is designed as the turnkey solution for photon BPM readout systems.

The AH501D is a 4-channel low noise and fast sampling rate bipolar picoammeter with an integrated bias voltage source and voltage analog monitors. It is composed by a transimpedance input stage for current sensing combined with a buffered output voltage circuit that allows users to monitor the input current behavior and level with a simple oscilloscope or a multimeter.

This device performs bipolar current measurements from ±2.5 nA (with a resolution of 300 aA) up to ±2.5 mA (resolution of 300 pA) with a minimum sampling period of 38.4 µs (equivalent to 26 kHz, for 1 channel and a 16-bit resolution).

The simultaneous sampling of the 4 independent channels makes this instrument ideal for beam position monitor readout as in the case of diamond detectors, ion chambers, photodiodes and blade gap-monitors.

Extremely low-noise bias source (up to 30 V) makes it the perfect fit for low-voltage biasing applications.

The presence of an internal low-noise (0.0005% of full scale) voltage source, ranging from 0 to 30 V, makes it extremely useful when using blade gap-monitors or diamond detectors needing a bias potential in order to increase the signal intensity and thus the signal-to-noise ratio. This built-in bias voltage source signal is available on a BNC connector and can also be set to a high-impedance state.

The AH501D is housed in a light and extremely compact box that can be placed close to the signal sources in order to reduce cable lengths and to minimize possible noise pick-up on the biasing and measuring signal paths. Low temperature drifts, good linearity and very low noise levels enable users to perform very high precision current measurements.

The AH501D picoammeter has an Ethernet 10/100 Mbit communication interface (TCP-IP and UDP) that allows easy instrument control with several programming languages and operating systems.

The AH501D has an external TRIGGER/GATE input signal on a coaxial LEMO connector in order to synchronize the acquisition of the picoammeter with external events – e.g. laser triggering. Furthermore, as for the other members of the CAEN ELS picoammeter family, digital samples can be transferred either using ASCII format or RAW binary data format for fast data transmission.

The Plug-and-Play solution for your Beam Position Monitor applications with dedicated Oscilloscope software.

Perform your current measurements, photon beam position and intensity computations and noise analysis with only one device!

Different detector geometries as well spectra analysis and data savings can be directly set, configured and analyzed on the GUI.


  • From ± 2.5 nA to ±2.5 mA current full-ranges
  • Up to 26 kHz sampling frequency
  • Internal 24-bit A/D conversion
  • Analog voltage monitors
  • Low-noise bias voltage source (up to 30V)
  • 120 fA full-scale range noise (typical)
  • 4-channel simultaneous sampling
  • Linear low-noise dual power supply PS2209 included
  • Standard Ethernet 10/100 Mbit communication interface (TCP-IP or UDP)

Technical specifications




Input Channels


Current Measuring Full-Scale Ranges

from ±2.5 nA to ±2.5 mA

Voltage Monitors

Yes (±5 V)

Current Polarity


Data rate

up to 26 ksamples/s


16 or 24 bit

RMS Noise (@RNG2, CIN = 5pF)

150 fA (maximum)

Bias Voltage RMS Noise



Ethernet 10/100 Mbit TCP-IP and UDP

I/O Signals

CONV output

Supply Voltage

from ±6 V to ±15 V

Bias Voltage Output

0 to 30V


155 × 165 × 42 mm


580 g

Input Connectors


Voltage Monitor Connectors

LEMO - Coaxial

Status Indicators

5 LEDs

Ordering options

Ordering code




AH501D – 4-channel Bipolar Picoammeter with Analog Monitors, Bias Voltage and +/-9 V Linear PS


Last reviewed: 2022-12-09 ⓘ More infoRevision: 1.8

Last reviewed: 2022-12-09 ⓘ More infoRevision: 1.1

Last reviewed: 2023-02-03 ⓘ More infoRevision: 2.0

Last reviewed: 2023-02-03 ⓘ More infoRevision: 1.0


Updated: 2023-01-24 - 111.02 MB ⓘ More info Version: 1.0
OS: Windows

Updated: 2023-02-03 - 325.29 kB ⓘ More info Version: 1.0
OS: LabView

Copyright CAEN ELS s.r.l.