FAQ
TL;DR: Use a 4‑wire hookup from the accelerometer to your differential‑input ADC; “connect the accelerometer output to the ‘positive’ input of the ADC.” [Elektroda, Steve Lawson, post #21670776]
Why it matters:** This FAQ helps sensor designers wire a single‑ended DC sensor into a differential‑input ADC with minimal added noise.
Quick Facts
- DC signals can’t use a transformer for SE→DIFF; transformers apply to AC only. [Elektroda, DAVID CUTHBERT, post #21670766]
- An “active phase inverter” creates the opposite polarity for DC and isn’t an amplifier by definition. [Elektroda, DAVID CUTHBERT, post #21670768]
- Practical wiring uses 4 lines: V+, sensor out, sensor ground to ADC–, and supply ground return. [Elektroda, Steve Lawson, post #21670776]
- “Amplifier” in this discussion can include a single‑transistor inverter or an op‑amp IC. [Elektroda, DAVID CUTHBERT, post #21670770]
- Optocouplers handle DC; consider only if isolation is also a requirement. [Elektroda, Ruben Proost, post #21670773]
What does “single‑ended to differential without amplifiers” actually mean?
You want two equal‑and‑opposite signals (or one signal plus a reference) from a single sensor output, without a voltage‑gain stage. The forum solution focuses on wiring and phase inversion rather than gain. This suits DC sensors like accelerometers. [Elektroda, DAVID CUTHBERT, post #21670768]
Can I do single‑ended DC to differential without an op‑amp?
Yes. Use an active phase inverter to generate the opposite polarity. “An active phase inverter will do it,” and it is not an amplifier by definition. This preserves DC levels while creating a complementary output. [Elektroda, DAVID CUTHBERT, post #21670768]
How do I wire a single‑ended accelerometer into a differential‑input ADC?
Use the 4‑wire method: sensor V+ to supply, sensor OUT to ADC+, sensor GND to ADC–, and a separate supply ground return. This creates a pseudo‑differential measurement that rejects cable noise. “Connect the accelerometer output to the ‘positive’ input of the ADC.” [Elektroda, Steve Lawson, post #21670776]
Can you give me the short 3‑step hookup?
- Run V+ from ADC supply to the accelerometer’s positive power pin.
- Wire the accelerometer OUT to ADC+.
- Wire accelerometer GND closely to ADC–, and return supply ground separately. [Elektroda, Steve Lawson, post #21670776]
Why won’t a transformer work for DC conversion?
Transformers require changing magnetic flux, so they pass AC, not steady DC. In the thread, the transformer suggestion applies only to AC signals, not to your DC accelerometer output. For DC, use wiring or active inversion methods. [Elektroda, DAVID CUTHBERT, post #21670766]
If I avoid op‑amps, can I still use a transistor stage?
Yes. The discussion frames solutions from a single‑transistor phase inverter up to an op‑amp. If you exclude op‑amps, a discrete transistor inverter remains valid for generating the opposite polarity. [Elektroda, DAVID CUTHBERT, post #21670770]
Will skipping amplifiers reduce noise into the ADC?
The OP sought to avoid amplifier noise (NSR). The advice given was to wire the sensor output to ADC+ and sensor ground to ADC–, using separate grounds to reduce pickup. This approach targets lower noise without adding active gain. [Elektroda, Elad Kadosh, post #21670775]
Do optocouplers help for single‑ended to differential DC?
Optocouplers handle DC, but the thread only notes that fact. They primarily provide isolation, not a balanced pair. Use them if you need isolation in addition to signal interfacing. [Elektroda, Ruben Proost, post #21670773]
What do “inverting” and “non‑inverting” inputs really mean on op‑amps?
They indicate phase relationship, not polarity. The plus sign means non‑inverting, and the minus sign means inverting. “It’s a misnomer to call the inputs ‘positive’ and ‘negative’.” This matters when describing connections. [Elektroda, Steve Lawson, post #21670774]
Which pin is the “positive connection” you mentioned for power?
It refers to the accelerometer’s positive power pin. The clarification was explicit: the suggestion meant the positive power connection on the accelerometer device you are using. [Elektroda, Steve Lawson, post #21670778]
My accelerometer is a chip on a PCB—does that change the hookup?
No. The guidance still applies. Identify the board’s V+, OUT, and GND pins and wire them as described. The OP confirmed the sensor was a chip mounted on a PCB, and the 4‑wire method addressed that setup. [Elektroda, Elad Kadosh, post #21670779]
Is one accelerometer output compatible with two ADC pins?
Yes. Connect the single output to ADC+, and connect the sensor ground to ADC–. The separate ground return completes the 4‑wire scheme and supports differential sampling without creating gain. [Elektroda, Steve Lawson, post #21670776]
Can I see a circuit picture for this setup?
The thread does not include a circuit picture. It provides verbal wiring steps and clarifications instead. You can sketch the 4‑wire diagram directly from those steps. [Elektroda, Elad Kadosh, post #21670765]
