New upgraded pA Metering Module

The product provides users with an easier way to evaluate system performance, and to validate their applications.

General Description

Accurate weak current signal measurement is critical for scientific analytic equipment, environmental monitoring and process control, which is a great challenge for design engineers especially when the weak current signal reaches pA or even fA level. Excelpoint’s new upgraded pA Metering reference design EPSH-PAM2.0 will provide users with an easier way to evaluate system performance, and to validate their prototype development.

EPSH-PAM2.0 is a full signal chain module: the current is input from the femtoampere level input bias current operational amplifier ADA4530-1 through to the ADA4522-1, as the buffering and/or gain setting stage, to the low noise 24-bit Sigma-Delta ADC, then to the Microchip ATSAML21 ultralow power ARM Cotex-M0+ MCU, finally connecting to PC via USB port. Through the specially designed Labview GUI, which provides module configuration function, features such as real-time waveform display, histogram and statistics analysis, and Excel test data export are provided. It can help achieve a better user experience.

Applications include:

• Laboratory and analytical instrumentation: spectrophotometers, chromatographs, mass spectrometers, pH meters, titrators, instrumentation, picoammeters, etc
• Environmental monitoring equipment
• PCB leakage measurement and ICT/FCT testing
• IVD
• Industrial process control
   

As per the block diagram in Figure 1, the module is powered up by PC USB connection. Two test points are to be provided for the measurements of ADA4530-1 output and AD7124-4 input separately.

Figure 1: Block diagram of the pA Metering Module. For a larger image, click here.

Key Features

• ADA4530-1 on the pA Meter Module is populated in transimpedance configuration with an input SMA connector that connects to amplifier inventing pin.
• By high value through-hole 10GΩ feedback resister, the output of ADA4530-1 will be 10mV for the relevant input current of 1pA after calibration (with default module setup).
• With low leakage design and shielding consideration, the EPSH-PAM2.0 module can reach high performance to satisfy most target applications.
• Linearity: Measured by Keithley 6220, within the range of 0–20pA, the linearity of the module can reach 0.9999 in steps of 1pA (uncalibrated).
• RMS noise: Measured by Keithley 6220, its performance is better than 550μV (equal to 55fA input current), and the rms noise background is less than 50μV (with SMA cap).
• Input current dynamic range: 0 to -200 pA.
   

For main chip highlights, refer to Table 1. Test results can be found in Figure 2. Figure 3 shows the waveform display and data of output value and RMS noise.

MPN	Description	Vendor
ADA4530-1	Femtoampere level input bias current operational amplifier	ADI
AD7124-4	Low power, low noise, completely integrated analog front end	ADI
LTC3260	Low noise dual polarity output power supply that includes an inverting charge pump with both positive and negative LDO regulators.	ADI
LT1762	Micropower, low noise, low dropout regulators	ADI
ATSAML21	MCU M0+ 48MHz	Microchip

Table 1: Chip highlights.

Figure 2: EPSH-PAM2.0 performance test data (by Keithley 6220). For a larger image, click here.

Figure 3: Waveform and test data (GUI). For a larger image, click here.

 

Ordering Part Number: EPSH-PAM2.0

Inside the pA module packaging box:

• One pA module hardware
• One SMA to BNC coaxial transfer cable
• One USB Type-C transfer cable
• One USB thumb drive containing document and GUI software
   

For more information, contact sales.enquiry@excelpoint.com.sg.