DMM - Lager

Read a bench digital multimeter (DMM) net. Calls go through the box’s hardware service, which owns the meter’s VISA session. A script and the CLI can use the same meter at once.

Import

from lager import Net, NetType

Methods

Method	Description
`measure(function, range=None, nplc=None, sensor=None)`	Configure and take one reading
`errors()`	Read and clear the meter’s error queue
`identify()`	Return the `*IDN?` reply

`Net.get(name, type=NetType.DMM)`

dmm = Net.get('VBAT', type=NetType.DMM)

`measure(function, range=None, nplc=None, sensor=None)`

Parameter	Type	Description
`function`	`str`	`dcv`, `acv`, `dci`, `aci`, `res`, `fres`, `cont`, `diode`, `freq`, `period`, `cap` or `temp`
`range`	`float` or `str`	Full-scale value in base units (`20` for 20 V, `2e-6` for 2 uF), or `None`/`"auto"` for auto-range
`nplc`	`float`	Integration time in power-line cycles; `dcv`, `dci`, `res`, `fres` only
`sensor`	`str`	Temperature probe for `temp`: `rtd:pt100`, `rtd:pt1000`, `ther:k`, …

Returns: float in V, A, ohm, Hz, s, F or degC, or None when the meter reports overload or an open input. Raises:

DMMUnsupportedError (a ValueError): the meter cannot do the function, range, NPLC value or sensor.
DeviceError (from lager.nets.device): the meter rejects a command or does not answer. The message carries the meter’s error.

The valid ranges and NPLC values per instrument are listed in the CLI reference.

Example

from lager import Net, NetType

dmm = Net.get('VBAT', type=NetType.DMM)

v = dmm.measure('dcv', range=20, nplc=10)
assert v is not None, 'VBAT over range'
assert 3.2 < v < 3.4, f'VBAT out of tolerance: {v:.6f} V'

r = dmm.measure('fres', range=200)
print(f'Shunt: {r:.4f} ohm')

if dmm.measure('cont') is None:
    print('Open circuit')