Chip Solutions for the New Generation of Digital Load Cells (DLC)

At the 2010’s Interweighing Trade Show acam presented already the “DLC 2.0” concept which was about the more convenient and simpler production and temperature adjustment procedure of digital load cells in comparison to the existing workflow. This year, on the 2011’s Interweighing Trade Show in Shanghai we took the concept further: thanks to PS09 and its integrated temperature unit a further simplification of the sensor can be done. For example, an only half-bridge based sensor can be used without any further external compensation resistor since the temperature compensation for gain and offset drift can be done by employing the chip’s internal temperature unit. Together with the previously existing high-end solution based on PS081 a whole range of Digital Load Cell types are feasible to build with PICOSTRAIN chip solutions now:

Low-cost OIML 3000 DLC
OIML 6000 DLC
High-end DLC

DLC-type 1: Low-cost OIML 3000

Features:

Suitable for OIML 3000
Only a single half bridge as sensor
Temperature drift compensation by integrated temperature measurement unit
Proven EMI immunity, well within 1e (10V/m)
Simple design – easy production
Simple 2-layer PCB
Lowest possible cost version of a DLC

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DLC-type 2: OIML 6000

Features:

Suitable for OIML 6000
Only a single half bridge as sensor
Temperature drift compensation by integrated temperature measurement unit
Proven EMI immunity, well within 1e (10V/m)
Simple design – easy production
Simple 2-layer PCB, same as OIML 3000 but with additional oscillator

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DLC-type 3: High-End

Features:

For highest resolution applications
No manual trimming of Rspan required
Easy to apply to existing load cells with full bridge
and compensation resistor
Proven EMI immunity
Build high quality DLCs
4-layer PCB

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Electromagnetic Interference (EMI):

All the DLC types introduced here were tested on a prototype-basis towards EMI (10V/m) and showed very good results. Thanks to the design of a digital load cell in general (electronics encapsulated in the load cell body) the interference level always stays well within 1e of the relevant specification. Therefore a DLC is a good solution for electromagnetically noisy environments.

>> See figures on the right

DLC Development Kit

For an easy entry into DLC design and a fast development acam provides a dedicated digital load cell PCB. The PCB comes together with an entire development kit, which also includes one load cell already equipped with the PCB to show full functionality by ‘plug-and-play’, but there is also a separate PCB to connect your own sensor.

The PCB offers many possibilities for evaluation and design-in, e.g. it is equipped with an external EEPROM for program development and several types of sensors can be connected, e.g. a half-bridge, a classical Wheatstone bridge or the PICOSTRAIN full-bridge.

DLC EMI performance

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Result in divisions @ 10V/M

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Result in µV @ 10V/M