FAQs

No. Pairing is a one-time operation in which Reader and Reel exchange Bluetooth IDs. After that, the Reader remembers the Reel, even if you switch Bluetooth off.

Yes, if you upgrade your DigiPro software to DigiPro2. DigiPro2 can import all of your classic surveys. After that, you can keep AT surveys and Classic surveys in the same project database; however, it is not recommended that surveys taken with one probe (classic or AT) be compared to initial readings taken by another probe (classic or AT).

No. The Classic probe is analog and the AT probe is digital. They have different power requirements and different readouts. Thus they are not freely interchangeable.

We do not recommend interchanging probes, in any case. Differences between probes are amplified by tilt and curvature of the casing, even with probes of the same type. The AT system features new cable marks and a cable gate, which introduces even more differences.

Best Practice: Some users obtain separate baseline surveys with two systems: an “active” system and a “backup” system. Subsequent surveys are taken with active system only. If that system fails, the backup system and its baseline survey can be used to continued the monitoring program. In this scenario, AT and classic systems would work well as either active or backup systems.

Yes, there are three main differences:

• AT cables are lighter and easier to carry, but permanently attached to the cable reel.
• AT cable marks are designed to work with a cable gate.
• AT cable marks are measured from the top wheels of the probe, rather than the middle of the probe.

The AT system displays readings as mm or inches of tilt, and this reading applies at the depth of the top wheels. Scroll downwards to see a technical explanation with a graphic. Classic cable marks are measured from the middle of the probe, but this has some unexpected effects when readings are plotted:

Metric Plots:

• AT system: A reading taken at 10 m is correctly plotted at 10 m, as you would expect.
• Classic system: A reading taken at 10 m is correctly plotted at 9.75 m, which you would not expect.

English Plots:

• AT system: A reading taken at 30 feet is correctly plotted at 30 feet, as you would expect.
• Classic system: A reading taken at 30 feet is correctly plotted at 29 feet, which you would not expect.

The cable gate provides an easy way to align cable marks to the top of the casing. With the pulley assembly, depth marks are typically aligned with the cleats at the top of the pulley, which is 0.3m or 1 foot above the top of the casing.

Metric Depths:

• AT system: When the cable mark shows 10 m, the probe is 10 m down hole.
• Classic system: When the cable mark shows 10 m, the probe is only 9.7 m down hole.

English Depths:

• AT system: When the cable mark shows 30 feet, the probe is 30 feet down hole.
• Classic system: When the cable mark shows 30 feet, the probe is only 29 feet down hole.

Summary: If classic surveys are not corrected for the pulley offset and the middle of the probe measurements, plots will show displacements a full interval deeper than they actually are.

The drawing shows a probe in tilted casing. We can overlay the probe with a right triangle. The vertical side of the triangle is the gravity vector. The hypotenuse of the triangle is the gauge length – the distance between the top and bottom wheels of the probe. You can see the tilt angle at the bottom of the triangle. The tilt angle applies anywhere along the length of L. The Digitilt DataMate displays readings in sine units (the sine of the angle of tilt), which also apply anywhere along the length of L. The AT Reader records sine units, but when it displays a reading, it multiplies the sine value by L, the gauge length of the sensor (500mm or 24 inches) to display a reading in mm or inches. This value applies only at the top of the triangle, as in the illustration, which is the elevation of the top wheels of the probe. Thus we measure cable marks from the top wheels of the probe, so that the reading is shown at the proper depth.

Yes. We strongly recommend that you start a new baseline, whether the replacement system is classic or AT. By starting a new baseline, you avoid the complications (rotation and sensitivity differences) that can appear when one probe is substituted for another. If starting a new baseline is not acceptable, you can achieve a better comparison by ensuring that the AT probe is positioned at the same elevation that the classic probe was. This would seem to be an easy task, but there are some details to consider. 

Different Indexes: To control the elevation of the probe, we align depth marks on the cable to an index. The AT system uses a cable gate. The cable gate aligns depth marks with the top of the casing, so we can say that the AT index is the top of the casing. With Classic systems, the index is often the top of the pulley assembly, which is 1 foot (0.3m) above the top of the casing. Thus for a given depth mark, the Classic

probe is actually 1 foot (0.3m) higher than the AT probe. 

Different Depth Marks: Depth marks on AT cable are measured from the top wheels of the probe. Depth marks on Classic cable are measured from the middle of the probe. The difference is 1 foot with English systems and 0.25m with metric systems. Thus for a given depth mark, the top wheels of the Classic probe are 1 foot (0.25m) higher than the elevation of the top wheels of the AT probe. 

Summary: Assuming that the pulley assembly is used as the index, the top wheels of the Classic probe are a 2 feet or 0.55m) higher than the the top wheels of the AT probe. Even if the Classic system uses the top of the casing as the index, the top wheels of the Classic probe are still 1 foot or 0.25m higher than the AT probe. If your Classic survey used a pulley assembly as index: Start the AT survey a full interval (0.5m or 2 feet ) shallower than the Classic survey. Also, edit the Classic survey to remove any depths shallower than 1m or 4 feet. If your Classic survey used the top of the casing as index: Make a short casing extension (0.25m for metric systems or 1 foot for English systems) to use with the AT cable gate. Now the AT probe will be held at the same depths as the Classic probe.

No, because that just isn’t practical. Here’s a suggestion:

1. Make a precise measurement of offset before you leave the office. Write down the measurements per the instructions in the manual.
2. Now you’re at the first inclinometer. Insert the instrument and take a measurement at the top of the hole. Note the inclinometer ID and measurement value on paper. Then do the normal spiral survey.
3. Now you’re at the next inclinometer. Repeat the steps above. You’ll probably see a slightly different value for the top of hole measurement. You shouldn’t see a huge difference. Be sure to note the inclinometer and the value. You can calculate the change later.
4. When you return to the office to crunch the data, you’ll have to enter the precise offset measurement. For the first inclinometer, you’ll enter the measurement as obtained at the office. For the other inclinometers, enter the precise measurement + the change from the top-of-hole measurement.

The spiral routine requires a minimum of two passes through the casing, but better results are obtained by four passes through the casing: the first oriented in the A0 direction, the second in the A180 direction, the third in the B0 direction, and the last in the B180 direction.

With English spiral sensors, readings must be taken at depths that are multiples of 5 feet. With metric spiral sensors, readings must be taken at depths that are multiples of 1.5 meters. This requirement affects the way you must record readings with the Digitilt DataMate. See instructions below.

Click this link to download the manual: Spiral Sensor Manual. Here are some abbreviated instructions.

1. Lower the spiral sensor to the bottom of the casing. Note the cable depth.

2. Choose Read – Record. Choose an installation, and step through the installation parameters.

3. Set Sens Type to Spiral.

4. Set Start depth to the multiple of 5 feet or 1.5 meters nearest to the cable depth that you noted in step 1. (For example, if the cable depth is 159 feet, set the start depth to 160 feet.)

5. Set End depth to 5 feet or 1.5 meters.

6. Take the first reading without moving the sensor. (In our example, the DataMate displays a start depth of 160 feet, even though the sensor is actually at 159 feet. The reading will be labelled 160 feet. This difference in depth has very little, if any, effect on the reading.)

7. The DataMake displays the next depth. This time raise the sensor to the indicated depth. (In our example, example, the DataMate prompts 155 feet. Raise the sensor to 155 feet and record the reading.

8. Continue taking readings at the prompted depths, rotate the sensor 180 degrees for the second pass. Then take readings in the B0 groove and finally in the B180 groove.

DigiPro2 can generate a graph from your spiral data. Use the graph to decide if the spiral is significant enough to affect your readings. If you decide to use the spiral data, DigiPro2 can generate a spiral corrections dataset. To generate a spiral corrections dataset, DigiPro2 needs the spiral data, the inclinometer ID (the spiral routine looks for the deepest and shallowest depth and the interval), and the precise offset measurement, number of passes, and the cable offset if available. See Spiral Correction in the DigiPro2 manual.