Meters
What each supported meter needs from you, and what the app does with it.
OWON XDM1041 and XDM1241
Two bench meters with the same SCPI command set: the XDM1041 is mains powered, the XDM1241 is its battery twin. Both talk over a CH340 USB serial bridge at 115200 baud, 8N1, with commands ending in a line feed. The app sets the mode and range itself and verifies the mode before it streams anything.
Connecting
- Plug the meter in over USB. On Windows the CH340 driver installs itself; on macOS 13 and later the port appears without a driver.
- In the app, open Instruments and choose the meter. If two CH340 ports are present, the app asks the meter who it is and picks the right one.
- Leave the meter on its front panel. The app hands the panel back when it disconnects.
What the app handles for you
- The firmware answers every set command with
OKlines, sometimes three at once. The app swallows them. - Some firmware swaps the readback of continuity and diode. The app learns the swap the first time it sets either mode and remembers it for the session.
- In diode and continuity the meter does not answer a range query, so the app never asks there.
- Auto ranging on DC volts moves up from the millivolt band but never back down. The app starts a small-signal step on the millivolt range before switching to auto.
- Resistance ranges of 5 MΩ and up switch the meter to its slow rate, and the next mode switches it back.
- In temperature mode the meter pauses for about three seconds every ten minutes to update its cold junction. The app waits it out.
- Over serial the meter updates two to three times a second whatever the rate setting says. Auto-capture needs three readings that agree, so a reading settles in about a second.
UNI-T UT61E+
A dial meter over a USB HID cable. The driver is not written yet, so the UT61E+ runs in manual mode today: the app names the mode, you turn the dial and type the reading. When the driver lands the app will read the mode flag from the stream and refuse a reading taken in the wrong mode, as it does for every dial meter.
Manual entry, for any meter
Type what the display shows. The app reads these forms and stores the value in the step’s base unit:
| You type | It reads |
|---|---|
0.41 | 0.41 in the step’s unit (volts on a diode step) |
1.2k or 1200 | 1.2 kΩ |
150mV | 0.15 V |
4.7u | 4.7 µF |
12,6 | 12.6 (a comma is a decimal point when there is no point) |
OL or open | An open circuit; the step’s range says whether that is a pass or a fault |
A unit from another mode is refused, so a resistance typed into a voltage step is caught before it is saved.
The calibration card
Diode readings differ between meters by tens of millivolts. Each meter measures the calibration card once; the app keeps an offset and a scale for that meter and applies them to its diode readings only, so the expected range on screen matches what your meter shows. The card ships with the bench kit. Overloads and every other mode pass through unchanged.
How a reading gets its verdict
Inside the expected range, a bound included, the reading is in range. Just outside a bound, within that bound’s check margin, it is a check. Beyond the margin it is a fault. A one-sided range only judges the bound it has, and an open reading takes whatever the tree’s author said OL means at that point: a fault on a diode check, in range on a resistance-to-ground check.