Current consumption as a function of pumping pressure.

Measuring the current consumed over a range of pressures was done by pumping against a fixed volume of water. As the pump ran the water pressure in the test stand increased which increase the load on the pump. Measurements of the electrical current consumed by the pump were made at a sequence of pressures. A lab power supply was used to supply current at 15.0V.

p	i	p	i
dbar	Amp	dbar	Amp
52	0.270	583	0.375
110	0.270	679	0.385
186	0.280	779	0.415
245	0.295	883	0.440
317	0.310	986	0.465
400	0.330	1093	0.500
486	0.345

A least-squares fit of the linear model,

$$i = \frac{di}{dp}p + i_o~,$$ (11)

yields $\frac{di}{dp}=0.224\frac{\textrm{mA}}{\textrm{dbar}}$ and i_o=243 mA with an RMS misfit of only 7 mA. Independent of supply voltage, the current consumed is a linear function of the pressure.