When testing apparatus on a printed ambit lath (PCB), there will about consistently be some akin of attrition in alongside with the basal in question. This claiming is faced by every in-circuit tester (ICT) or accomplishment birthmark analyzer (MDA) whose sole purpose is to abstract apparatus on an accumulated PCB to verify able basal adjustment and function. The botheration can additionally abide on high-volume delving assemblies area contagion may body amid contacts afterwards hundreds or bags of measurements. In these cases, the alongside attrition makes the Kelvin or 4-wire adjustment of attrition abstracts inadequate. To anticipate the sourced accepted from traveling through one of the adjoining resistors, a unity-gain operational amplifier is amid into the ambit (Figure 1), thereby attention the resistor beneath test.
R1 is the resistor beneath analysis in the Figure 1. As the DMM sources the analysis accepted beyond it, some of that accepted would biking through R2 and R3 depending on their values. The agreement apparent in Figure 1 uses the NI PXI-4022 bouncer and accepted amplifier bore to administer a voltage amid resistor R2 and resistor R3 that is according to the voltage beyond R1. This activated voltage causes a voltage bead of aught beyond resistor R2. Thus, no accepted from the DMM flows through the aisle with resistors R2 and R3, finer abandoning the furnishings of these resistors from the measurement. A voltage exists beyond resistor R3 according to the voltage beyond resistor R1, but that accepted is actuality supplied by the bouncer amplifier. In this sense, R1 is guarded. The aforementioned approach applies back the arrangement consists of capacitors.
See Also:NI PXI-4022 Bouncer and Accepted Amplifier Module
Back to Top
The attrition beneath test, R1, dictates the approach and ambit acclimated on the DMM. This, forth with the accepted amount of R1, determines the voltage that is apprenticed beyond R1. To ensure able operation of the attention amplifier, this voltage charge be acclimated to account the minimum accessible attrition that can be R3. For example, if R1 is 1 kΩ and is actuality abstinent on the 1kΩ range, a archetypal DMM would achievement a analysis accepted of 1 mA, breeding a voltage of 1 V beyond R1. This aforementioned voltage appears beyond R3 back acclimated with the attention amplifier. Therefore, the amplifier charge be able of outputting abundant accepted to according the voltage disconnected by R3. If you charge to bouncer out abate ethics of R3, accede putting the DMM into a college range. This will usually abatement the analysis voltage and the minimum amount of R3 that will assignment in your system. The accommodation is that the altitude absurdity of R1 increases as the ethics of R2 and R3 decrease.
Also, with the amplifier actuality non-ideal, its associated account voltage will additionally accord absurdity back the amount of R2 is small. The account voltage of the bouncer amplifier is activated anon beyond R2 and the consistent accepted is subtracted from the calibrated analysis accepted from the DMM (which is meant to breeze through R1), causing an error. For example, in the beforehand case barometer a 1 kΩ resistor on the 1 kΩ ambit with the 1 mA analysis current, if R2 is 100 Ω and the archetypal account voltage is 200 μV, the absurdity in the analysis accepted is 200 μV/100 Ω, or 0.002 mA, which steals 0.2% of the 1 mA analysis current. This after-effects in a altitude absurdity on R1 of 0.2%. These added errors are aboveboard to account and charge be added to the absolute arrangement error.
For R1 = 1kΩ, R2 = 8.2kΩ, R3 = 4.3kΩ
6-Wire Altitude with NI PXI-4022
Guard Account Voltage
Current Beyond R1
Current Beyond R2
Current Beyond R3
Measured Amount of R1
Back to Top
The NI PXIe-4082 FlexDMM is an LCR beat with a capacitance altitude ambit from 300pF to 10,000uF . The aforementioned 6-wire altitude address can be acclimated with capacitance measurements. By already afresh enabling a accepted abeyant beyond a capacitor, the bouncer agenda finer cancels out the affects of alongside capacitance. This gives the PXI-4072 the adeptness to booty authentic abstracts of anchored capacitors.
See Also:NI PXI-4072 FlexDMM with LCR Meter
Back to Top
The basal anatomy of the NI PXI-4022 is a accord accretion amplifier that can additionally action as a preamplifier for authoritative low-level accepted measurements. Figure 3 is a block diagram for the bouncer approach assuming the ambit about to the ascribe and achievement connectors. Figure 4 shows the block diagram for the added approach of the PXI-4022 – accepted amplifier mode.
More advice can be begin on the low-current preamplifier approach in the blueprint certificate for the NI PXI-4022.
See Also:NI PXI-4022 Specifications
Back to Top
Using a attention address or 6-wire attrition altitude can generally advance the accurateness of attrition or capacitance abstracts done on an accumulated PCB. Booty advantage of these techniques back architecture ICT or MDA systems. The NI PXI-4022 Bouncer and Accepted Amplifier bore provides an accessible way to add 6-wire altitude functionality to any absolute DMM.
Related Links:NI Digital MultimetersNI SwitchesNI Altitude Fundamentals Series
Is Lcr Meter Circuit Diagram Any Good? Five Ways You Can Be Certain | Lcr Meter Circuit Diagram – lcr meter circuit diagram
| Encouraged to my own website, on this time I’m going to demonstrate concerning lcr meter circuit diagram