Calibrate teachpoints on the Agilent Bravo

A fresh Bravo doesn't know where its 9 deck locations are. Each location has a teachpoint, an X, Y, and Z position in millimeters that the head moves to. The Liquid Handling SDK loads the teachpoints from the connector when it configures the Bravo, so calibrate them once before the first pipetting run, and again after the Bravo or a deck accessory moves.

Prerequisites

• An Agilent Bravo, powered on, with its connector installed and initialized
• One tip of the type you'll pipette with, for example an Agilent 250 µL tip (LT250) on a 96LT head
• A clear deck, apart from accessories that stay on it, such as a shaker
• Access to the Bravo in the Platform's Devices page or in GroundControl's Operations tab

How the axes move

Every position is in millimeters. After homing, the head sits at the top of Z, and positions read close to zero, for example 0.0001. That's expected, and it's the safest position to start from.

Put a tip on the A1 nozzle

1. In the gripper's Movement Controller, run Retract. The head only moves with the gripper retracted.
2. Put one tip on the A1 nozzle by hand. When you set the teachpoints, you name the tip type, and the connector adds that tip's length to the measured Z. The teachpoint then doesn't depend on the tip you calibrated with.
3. Your hand breaks the light curtain, and the Bravo switches its motors off. Run Enable All Axes in the Device Controller before the next move. See Recover from a stop.

Bring the tip to the cross

Each deck location has a cross that marks its teachpoint. Pick a location with nothing on it, for example location 1, and note its number. You'll enter it when you set the teachpoints.

1. Keep Z at the top while you move in X and Y. For larger steps, run Move By in the head's Movement Controller with Z and W at 0, which leaves those axes where they are. For small steps, run Jog in the deck's Calibration Service on BravoX or BravoY.
2. Stop when the tip is right above the center of the cross. Check from the front and from the side.
3. Jog BravoZ down with a distance of 1 and the default velocity of 10 mm/s. A positive distance moves the head down.
4. Repeat, and wait for each jog to finish before you send the next one. The connector runs one jog at a time and rejects another while one is running.
5. When the tip is a few millimeters above the cross, use smaller distances until the tip just touches its center.

Set the teachpoints

Both commands read the head's current position and take the same three inputs:

Calibrate Teachpoints sets all 9 locations from the one you're at. Use it on a fresh Bravo, or after the whole Bravo moved.

The Bravo deck is a 3 by 3 grid with fixed spacing, 186.69 mm between columns and 109.093 mm between rows. So the connector works out the other 8 positions from yours, and every location gets the same Z.

Calibrate Single Teachpoint sets only the location you're at. Use it for a location that sits higher or lower than the rest of the deck, for example one that holds a shaker or another device: bring the tip to that location's cross, then run it for that location.

Check the teachpoints

1. In the deck's Calibration Service, read Teachpoints and check the X, Y, and Z of each location.
2. Restart the connector and read Teachpoints again. The values should be the same, which confirms the connector saved them.

A Z value that's too low makes tip pickup fail, because the head reaches teachpoint Z plus 1.8 mm. If a tip touches the well bottom at a low dispense height, recalibrate that location's Z with Calibrate Single Teachpoint.

Then confirm from Python that the SDK loads the teachpoints:

from unitelabs.sdk import AsyncApiClient
from unitelabs.liquid_handling.agilent import Bravo

client = AsyncApiClient()
bravo = Bravo(name="Bravo", client=client)

# configure() loads the teachpoints from the connector
await bravo.configure()
for location in range(1, 10):
    print(location, bravo.deck.get_teachpoint(location))

Expected: 9 locations, each with the X, Y, and Z you saw in Teachpoints.

Set the gripper offset

If the gripper picks up plates off-center front to back, run Set Gripper Y Offset in the gripper's Calibration Service. The offset is in millimeters, and a positive value moves the gripper forward. The connector saves it to config.json.

Next steps

• Recover from a stop: what to do after a light-curtain break or an emergency stop.
• Tip handling: pick up and drop tips with the calibrated deck.