What might cause a CS616 or CS625 signal to keep reading -6999?
The CS616/CS625 is not receiving power. Ensure that the red wire is well connected to 12V and that the black and clear wires are both connected to G. Also check that the orange wire is well connected to a control port and that the data logger program references that control port as part of the sensor measurement.
The data logger is not receiving a signal from the CS616/CS625. Ensure that the green wire is well connected to a single-ended analog input channel and that the data logger program references that channel in the CS616() or PeriodAvg() instruction.
The soil is too conductive. If the soil has high electrical conductivity, high clay content, or high organic matter content and the CRBasic instruction CS616() or Edlog instruction P138 is used, the period might be out of range for that instruction. In that situation, it may be possible to use PeriodAvg() or P27 as shown in the program examples of the CS616 and CS625 instruction manual.