A few occasional times when the penis is unable to get an erection does not necessarily mean that you are suffering from impotence, but it could also be a psychological factor. Many men are not sure whether they are suffering from impotence or not, but in fact you can determine the nature of impotence from the nocturnal erection of the penis. Normal men of all ages can have reflex penile erections during sleep at night. Adolescents have an average of about 6 erections per night, each lasting 20-30 minutes; young adults have an average of about 4 erections per night; and healthy seniors over 65 years of age can still have a total of 1 to 1.5 hours of erections per night. Even children often have penile erections in their sleep. Obviously, nocturnal penile reflex erection is not related to sexual stimulation and is not affected by psycho-psychological factors, therefore, it can be used to identify whether impotence is due to psycho-psychological factors or due to disease factors. If the impotence patient has no nocturnal erection or the degree of erection is below the normal value of the same age group, there may be disease factors, and further in-depth identification of the root cause of the disease is required. If the impotence patient has normal nocturnal erection, it will not be caused by disease factors, but mental and psychological factors at work. Self-determination of penile nocturnal erection has the following methods: Penile circumference measurement: There is a commercially available tape measure (general paper), one end of the side of a square buckle, before going to bed will be around the penis, one end of the buckle from the wear out, the first read down the penis in the soft state of the circumference of the base, and then look at the data the next morning there is no change. The difference between the data before going to bed and after waking up is the increase in the circumference of the penis after erection at night. In normal people, the increase is 1.5 to 4.1 centimeters. If greater than 1.5 centimeters, the impotence may be due to mental factors; greater than 1.5 centimeters, the impotence may be due to mental factors; less than 1.5 centimeters, we should think that it may be due to disease factors. Stamp test: four perforated stamps around the body of the penis, the overlapping part of the adhesive, so that it forms a ring after sleep. In the morning, the stamps are examined for tears at the perforations, which indicate a nocturnal erection. Penile Strength Measurement: Use a commercially available paper penile strength measuring tape and tape it around the penis before going to bed, and the next morning observe how the three small ribbons on the tape break. If none of the bands break, there is no nocturnal erection and impotence is due to disease. Only break the red ribbon for ineffective erection, break the red and yellow ribbon for insufficient erection, the cause of impotence should still be considered disease factors. If the red, yellow, blue three small color band all broken, that night erection is good, impotence is due to mental and psychological factors. In recent years, there is a novel instrument to monitor penile erection at night, the use of an elastic force sensing ring on the penis to fall asleep, the ring can automatically monitor and record penile erection at night, the next day to inform the computer processing can be made after the graphic report. Of course, this method should be carried out under the supervision of a doctor. Obviously, in the impotent person self-measurement of nocturnal penile erection, to identify the cause of impotence is very helpful. Certain patients with psychogenic impotence, seeing that the penis can be normally erected at night, the confidence is greatly increased, and the impotence is not cured.