The well fluid pressure increases as the flow fluid flows upward through impellers 81 and diffusers 73. To contain this fluid pressure, each dillliser 73 has an annular seal 89 surrounding  the  outer  diameter  of  dillliser  shroud  75 in

sealing engagement with housing bore 49. Optionally, an annular recess 91 may extend around the outer diameter of each diffuser shroud 75.

Lower instrument sub 23, as well as upper instrument sub 33, has a number of sensors 93 for sensing various param- eters. These parameters include, but are not limited to, well fluid pressure, temperature, gas content, viscosity, gas per- centage, and oil/water ratios. Other parameters include vibration, and shaft proximity to other structures. Sensors 93 may be of a variety of types and may be electrical or electronic, or they may be fiber optic  types.

In this example, a sensor 93a is illustrated schematically as being mounted in one of the diffuser flow passages 79 adjacent the intake of one of the impellers 81. Another sensor 93b is illustrated as being mounted in the diffuser flow passage 79 directly above and in the discharge of the same impeller 81. Thus sensor 93b is located in the next upward dillliser 73 from sensor 93a in this   example.

For each sensor 93, a diffuser sensor port 95 extends from the particular dillliser flow passage 79 through and to the outer diameter of one of the dillliser shrouds 75. Although diffuser sensor ports 95 are shown extending radially, they could extend at other angles relative to axis 51. Each diffuser sensor port 95 leads from one of the sensors 93 to a point generally  180 degrees from motor lead recess 55.

A longitudinal groove 97 has an upper end that registers with sensor line port 71 (FIG. 4). Longitudinal groove 97 extends downward parallel to axis 51 and makes intersec- tions with diffuser sensor ports 95. Groove 97 extends downward past at least one of the diffuser annular seals 89, and in the example shown, past two of them. In this embodiment, groove 97 is a straight open recess formed on the inner surface of bore 49 of housing 47. Alternately, groove 97 could be formed on the outer diameters of diffuser shrouds 75.

Sensor line 43 extends through sensor line port 46 and down longitudinal groove 97. Sensor line 43 bends at the junction with one of the diffuser sensor ports 95 and extends to sensor 93a. be same or a different sensor line 43 extends

4O to sensor 93b. Once sensor lines 43 have been installed, a sealant 99 is pumped down sensor line port 46 and longi- tudinal groove 97. Sealant 99 flows along groove 97 past the junctions with dillliser annular seals 89. Sealant 99 may also enter and even fill dillliser annular recesses 91. Sealant   99

43 cures, blocking any leak paths past dillliser annular seals 89. As an alternate to sealant 99, jogs could be machined around any junctions of groove 97 with diffuser annular seals 89. Although only two sensors 93 are shown, each instrument sub could contain others. For example, as illustrated in US 2013/0148127, optic fiber sensors could be located at thrust washers 85 and 87 to monitor thrust. Sensors could also be located at the interfaces between shaft 51 and dillliser hubs 77 to monitor vibration. Sensors could also be located in the annular  recesses  91 to  monitor  temperature  and pressure

within this area.

While the disclosure has been shown and described in only a few of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the disclosure.

60 The invention claimed is:

1. An electrical submersible pump assembly, comprising: a centrifugal pump;

an electrical motor operatively coupled to the  pump;

a seal section disposed between the pump and the  motor