Clock calibration of remote systems by roundtrip time

A well measurement system comprising:

• a downhole tool, wherein the downhole tool comprises:
• a first device;
• a master module disposed on the first device, wherein the master module comprises a master transmitter and a master receiver;
• a second device;
• a module disposed on the second device, wherein the module comprises a transmitter and a receiver;
• and
• an information handling system for:
• transmitting a signal to the module,
• changing the master module from a line driver controlled by the master transmitter to a line receiver controlled by the master receiver,
• transmitting a return signal from the module to the master module
• determining Tdd of a time for the signal to travel from the master module to the module, wherein the Tdd=(Counter-Tf-T4-T3)/2, wherein the Counter is a second time for the signal to travel from the master module to the module and back to the master module as measured by the master module, the T4 is a master module signal detection time, the Tf is a fixed time delay and the T3 is a module signal detection time,
• determining T2, wherein the T2=T3+(Tdd-T1), wherein the T2 is a time delay and the T1 is a time it takes for the signal to be transmitted and detected at the master module,
• receiving the return signal from the module with the master module, and
• measuring a time for the signal to travel from the master module to the module and the return signal back to the master module.

A method for calibrating a downhole tool, comprising:

• disposing the downhole tool in a borehole, wherein the downhole tool comprises a first device and a second device;
• transmitting a signal from a master module disposed on the first device to a module disposed on the second device;
• transmitting a return signal from the module to the master module after a fixed time delay;
• receiving the return signal with the master module;
• measuring a time for the signal to travel from the master module to the module;
• determining Tdd of the time for the signal to travel from the master module to the module, wherein the Tdd=(Counter-Tf-T4-T3)/2, wherein the Counter is a time for the signal to travel from the master module to the module and back to the master module as measured by the master module, the Tf is the fixed time delay, the T4 is a master module signal detection time, and the T3 is a module signal detection time;
• determining T2, wherein the T2=T3+(Tdd-T1), wherein the T2 is a time delay and the T1 is a time it takes for the signal to be transmitted and detected at the master module.

A method for calibrating a downhole tool, comprising:

• disposing the downhole tool in a borehole, wherein the downhole tool comprises a first device and a second device;
• transmitting a signal from a master module disposed on the first device to a module disposed on the second device;
• transmitting a return signal from the module to the master module after a fixed time delay;
• receiving the return signal with the master module;
• measuring a time for the signal to travel from the master module to the module;
• determining Tdd of the time for the signal to travel from the master module to the module, wherein the Tdd=(Counter-Tf-T4-T3)/2, wherein the Counter is a time for the signal to travel from the master module to the module and back to the master module as measured by the master module, the Tf is the fixed time delay, the T4 is a master module signal detection time, and the T3 is a module signal detection time;
• determining T2, wherein the T2=T3+(Tdd-T1), wherein the T2 is a time delay and the T1 is a time it takes for the signal to be transmitted and detected at the master module;
• and
• counting a number of transmitter clock ticks during the time for the signal to travel from the master module to the module and back to the master module.

A method for calibrating a downhole tool, comprising:

• disposing the downhole tool in a borehole, wherein the downhole tool comprises a first device and a second device;
• transmitting a signal from a master module disposed on the first device to a module disposed on the second device;
• transmitting a return signal from the module to the master module after a fixed time delay;
• receiving the return signal with the master module;
• determining Tdd of the time for the signal to travel from the master module to the module, wherein the Tdd=(Counter-Tf-T4-T3)/2, wherein the Counter is a time for the signal to travel from the master module to the module and back to the master module as measured by the master module, the Tf is the fixed time delay, the T4 is a master module signal detection time, and the T3 is a module signal detection time;
• determining T2, wherein the T2=T3+(Tdd-T1), wherein the T2 is a time delay and the T1 is a time it takes for the signal to be transmitted and detected at the master module;
• counting a number of transmitter clock ticks during the time for the signal to travel from the master module to the module and back to the master module;
• and
• applying an error adjustment with the T2.