Liquid Classes

Liquid classes define the plunger physics — calibration, per-phase speeds, and air gaps — used during aspirate and dispense. EvoLiquidClass is shared by both EVO arms (the MCA and, for instruments with one, the LiHA); today only the MCA96 head is implemented in the SDK, so in practice every liquid class you use targets it. The labware library also ships 42 of EVOware's own liquid classes, importable from unitelabs.labware.tecan.liquids — it's often easier to start with one of these than to build your own from scratch (see Using a Predefined Liquid Class).

Prerequisites

• Basic understanding of the EVO pipetting operations (See Basic Pipetting)

Default Liquid Class

If no liquid_class is passed to aspirate()/dispense(), an uncalibrated EvoLiquidClass() is applied — factor 1.0, offset 0.0, and the class's own default speeds.

from unitelabs.labware.tecan import EvoLiquidClass

await evo.mca.aspirate(source_trough, volume=100, liquid_class=EvoLiquidClass())

Using a Predefined Liquid Class

Import one of the 42 liquid classes shipped in unitelabs.labware.tecan.liquids instead of writing your own. Each is a direct import of one EVOware <SubClass>, so its tip/min_volume/max_volume band is already set correctly for that class — pick the one matching the liquid, tip family, and volume you're pipetting.

from unitelabs.labware.tecan.liquids import Evo_Water_WetContact_MCA_DiTi_20p01_200p01

await evo.mca.aspirate(
    source_trough,
    volume=100,
    liquid_class=Evo_Water_WetContact_MCA_DiTi_20p01_200p01(),
)

Volume Calibration

EvoLiquidClass applies an affine correction to the sample volume only — never to air gaps or the excess volume:

corrected = target_volume * calibration_factor + calibration_offset

import dataclasses
from unitelabs.labware.tecan import EvoLiquidClass
from unitelabs.labware.math import Decimal


@dataclasses.dataclass
class WaterHighVolume(EvoLiquidClass):
    calibration_factor: Decimal = dataclasses.field(default=Decimal("1.0074"))
    calibration_offset: Decimal = dataclasses.field(default=Decimal("0.0"))


await evo.mca.aspirate(source_trough, volume=100, liquid_class=WaterHighVolume())

Restricting to a Tip Type and Volume Band

tip, min_volume, and max_volume are metadata only — nothing auto-selects a liquid class based on them. Passing a class whose band or tip doesn't match what's mounted produces a warning, never a substitution.

import dataclasses
from unitelabs.labware.tecan import EvoLiquidClass, EvoTip_MCA_DiTi_200
from unitelabs.labware.math import Decimal


@dataclasses.dataclass
class Water200uL(EvoLiquidClass):
    tip: type = EvoTip_MCA_DiTi_200
    min_volume: Decimal = dataclasses.field(default=Decimal("2.0"))
    max_volume: Decimal = dataclasses.field(default=Decimal("220.0"))

liquid_class = Water200uL()
liquid_class.check_tip(mounted_tip)  # warns if mounted_tip isn't an EvoTip_MCA_DiTi_200
liquid_class.compute_corrected_volume(target_volume=250)
# UserWarning: Water200uL is calibrated for volumes in [2.0, 220.0) µL, received 250 µL.

Aspirate Parameters

Every liquid class defines the following parameters, consumed via aspirate_parameters when a pipetting step compiles:

Dispense Parameters

Mapping from EVOware

One EvoLiquidClass instance corresponds to one EVOware <SubClass>. EVOware groups several sub-classes — each valid for one tip type and one volume band — under a single named liquid class; this SDK flattens that structure into tip + min_volume/max_volume on separate classes, one per sub-class. Only <Single> (single-pipetting-mode) values are modeled; EVOware's multi-pipetting mode is not supported.

Checking Tip Compatibility

tip = evo.mca.get()
liquid_class = Water200uL()
liquid_class.check_tip(tip)
# UserWarning: Water200uL is calibrated for EvoTip_MCA_DiTi_200, received EvoTip_MCA_DiTi_50.

check_tip() is informational only — pipetting proceeds regardless of a mismatch; it does not raise.