Install casing as straight and as vertical as possible to avoid systematic errors.
It is useful to install the casing deep enough for 5 to 10 measurement depths in stable ground. Readings from this part of the casing will help you detect and correct systematic errors.
Terminate the top of the casing so that you can use a pulley assembly.
Mark the A0 groove with paint or a notch. Train technicians to start the survey with the uppermost wheel of the probe in this groove.
Survey new installations two or three times. Choose one of them to be the initial. Typically, the second or third survey will compare better with subsequent surveys.
Using the Probe
Use the same probe for each survey, if possible. If you must use a different probe, be sure to note the serial number of the probe used for each data set so any necessary corrections can be made during data processing.
Protect the probe from shock, which contributes to zero shift and sensor rotation. Transport the probe in its carrying case. Try to cushion the case. Power up the probe before you lower it into the borehole. Do not allow the probe to strike the bottom of the borehole. When you lift the probe out of the casing, do not allow the wheels to spring out. Instead, clamp your hands over the wheels and release the wheel carriage gradually.
Perform regular maintenance: See Inspection and Maintenance of the Digitilt Probe.
Handling Control Cable
Use the same control cable for each survey, if possible.
When very high precision is expected and the installations show significant curvature (a J-shaped profile, for example), it may useful to periodically record the date and the precise length of your control cable.
When you connect control cable to the probe, avoid overtightening the nut, since this will flatten the O-ring and reduce its effectiveness.
Use the same control cable for each survey, if possible.
Use a pulley assembly, if possible, with the Classic Inclinometer system. Use the cable gate, if possible, with the Digitilt AT system. It protects the control cable and provides a good reference index.
Use a consistent top reference. The goal is placement repeatability within 5 mm or 1/4 inch. If one technician uses a pulley/cable gate and another technician does not, probe positioning will be inconsistent, and data will have to be manipulated before it is useful.
Always draw the probe upward to the reading depth. If you accidentally draw the probe above the intended depth, lower the probe down to the previous depth, then draw it back up to the intended depth. This technique ensures the probe will be positioned consistently.
Getting Good Readings
Use the same probe for each survey, if possible.
Wait 10 minutes for the probe to adjust to the temperature of the borehole.
Wait for displayed readings to stabilize. The DataMate displays 3 diamonds and the Digitilt AT displays either “Pull” or “Tap” in green when readings have stabilized within two units. Note: you must always wait 10 minutes for temperature adjustment even if the readout shows the readings have stabilized.
